Intelligent signaling scheme for computer-readable medium for H.323 mobility architecture

ABSTRACT

The present invention provides an intelligent signaling scheme for a computer-readable medium for an H.323-based mobility architecture for real-time mobile multimedia communications and conferencing over packet-based networks. The steps for the scheme include: (1) upon becoming mobile and initiating an H.323 communication that includes at least one of: audio, video and data, by the Mobile Entity, with respect to notification, one of providing, by at least one of a plurality of available H.323 Home/Foreign Mobility Gatekeepers, notification of H.323 mobility services availability by periodically broadcasting, multicasting or unicasting a Mobility Gatekeeper Advertisement with a multicast/unicast address; and where the Mobile Entity lacks notification of H.323 mobility services availability, broadcasting, multicasting, unicasting or sending, by the Mobile Entity, a message to the Home Gatekeeper or Home Location Database, which notifies H.323 Home/Foreign Mobility Gatekeepers in a preselected area local to the Mobile Entity that the Mobile Entity needs H.323 mobility services and notifying, by the H.323 Home/Foreign Mobility Gatekeepers, the Mobile Entity of available H.323 Home/Foreign Mobility Gatekeepers; (2) registering, by the Mobile Entity, with a H.323 Home/Foreign Mobility Gatekeeper of the available H.323 Home/Foreign Mobility Gatekeepers that support H.323 mobility services in a Location Area, Cell or Zone of the Mobile Entity; and (3) providing, for the Mobile Terminal, Node or Entity by the H.323 Home/Foreign Mobility Gatekeeper with which the Mobile Entity is registered, support for the H.323 communication that includes at least one of: audio, video and data.

RELATED FILINGS

This application claims the benefit of U.S. Provisional Application No.60/154,212, filed Sep. 16, 1999, which is hereby entirely incorporatedherein by reference and two concurrently filed applications “H.323Mobility Protocol for Terminal User and Service Mobility” applicationSer. No. 09/642,229 pending and “H.323 Mobility Architecture forTerminal User and Service Mobility” application Ser. No. 09/642,142Pending, both of which were invented by Radhika R. Roy.

FIELD OF THE INVENTION

The present invention relates generally to the H. 323 standard fortransmitting audio and video data streams, and more particularly toextending the H.323 standard to support mobility in a multimediacommunication system with services over packet-based networks.

BACKGROUND OF THE INVENTION

Originally, the International Telecommunications Union (ITU) developedH.323 as an adaptation of H.320, which addresses videoconferencing overISDN and other circuit-switched networks and services. H.320 wasratified in 1990, and corporations expanded their networks to includeLocal Area Networks (LANs) and LAN gateways to the Wide Area Network(WAN). Then, H.323 was expanded beyond being an extension of H.320 sothat H.323 now covers the corporate intranets and packet-switchednetworks in general. The ITU published a set of standards for multimediacommunication over packet-based networks (PBNs) under the H.323designation, which includes standards for data channels, monitoringchannels, and control channels. It includes provision of real-timeaudio, video and/or data communications. The H.323 components defined bythe standard include: terminals, gateways, gatekeepers and multipointcontrol units (MCUs). The terminals provide real-time communications,must support audio/voice communications and optionally support data andvideo. The most common H.323 terminals are the applications that run ona personal computer (PC). H.323 gateways provide services to H.323clients and allow communication with non-H.323 entities, such ascommunication between H.323 terminals and telephone in acircuit-switched network. Gatekeepers provide call control services forH.323 endpoints, e.g., address translation and bandwidth management.Gatekeepers are optional in the H.323 standard, but, if they arepresent, the endpoints must use the services of the gatekeepers. TheH.323 standard specifies certain mandatory services that gatekeepers, ifutilized, must provide. The multipoint control units provide support forconferences of three or more endpoints by managing conference resources,manage negotiations between the endpoints to specify which audio orvideo codec(s) to use and may manage the media stream. The H.323standard defines how audio and video conferencing systems communicateover packet-switched networks defines call control and managementpractices for point-to-point and broadcast/multicast/unicast multipointconferences, addresses QoS issues with a centralized gatekeeper that LANadministrators use to manage media traffic, bandwidth and userparticipation, and describes functionality that allows calls to connectfrom the LAN to the Public Switched Telephone Network (PST) as well asto other H.32x standards-based terminals.

In version 2 of the H.323 standard, video and audio data streams arecompressed and packetized in accordance with a real-time transportprotocol (RTP/RTCP) standard from the Internet Engineering Task Force(IETF) and are used to support video conferencing and othercommunications over the Internet. Packets include data and headerinformation which facilitates detection of packet loss, detection ofpacket status and synchronization of the packets. The video data streamsmay use H.261, H.262, or H.263 protocols. Audio data streams may useG.711, G.722, G.723.1 G.728 or G.729 protocols. Generally, the H.323standard supports teleconferencing in networks that utilize TCP/IP, suchas, for example, the Internet.

The H.323 system supports interoperability and assumes that users,terminals, and services are fixed. If an H.323 terminal is moved formone network to another, its point of attachment or network addresschanges. In this situation, the address of the mobile terminal needs tobe resolved to set up a new call or continue a same call. Thus, there isa need for an H.323 mobility architecture that provides for terminal,user and service mobility.

SUMMARY OF THE INVENTION

The present invention provides an intelligent signaling scheme for acomputer-based medium for an H.323-based mobility architecture forreal-time mobile multimedia communications and conferencing overpacket-based networks wherein a plurality of H.323 mobility gatekeepersprovide notification of H.323 mobility services availability byperiodically multicast, broadcasting, and/or unicast a MobilityGatekeeper Advertisement with a multicast/unicast address asappropriate. If needed, the mobile Terminal/Node/Entity can alsomulticast, broadcast, and/or unicast a discovery message seeking agatekeeper that provides the mobility services. The protocol includesthe steps of detecting, by a Mobile Terminal/Node/Entity, whether it haschanged its location in a given zone or domain where zone and(administrative) domain have been defined in accordance to ITU-TRecommendations H.323 and H.225.0. The abstraction of zone is such thatit is managed by a gatekeeper while a domain consists of one or morezones. A domain may be administered by an administration (e.g., anInternet Service Provider (ISP), a corporation, a carrier network,etc.). The communications between the domains are via border elements(BEs). However, the border elements can communicate with the gatekeeper.

The invention provides a computer-readable medium havingcomputer-executable steps for implementing, by a MobileTerminal/Node/Entity, an H.323-based mobility protocol for real-timemobile multimedia communications and conferencing over packet-basednetworks wherein a plurality of H.323 mobility gatekeepers providenotification of H.323 mobility services availability by periodicallybroadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisementwith a multicast address. The computer-executable steps typicallyinclude: where the Mobile Terminal/Node/Entity becomes mobile andinitiates an H.323 communication that includes at least one of: audio,video and data, by the Mobile Terminal, Node or Entity, with respect tonotification, one of providing, by at least one of a plurality ofavailable H.323 Home/Foreign Mobility Gatekeepers, notification of H.323mobility services availability by periodicallybroadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisementwith a multicast/unicast address; and the Mobile Terminal/Node/Entitylacks notification of H.323 mobility services availability,broadcasting, multicasting, unicasting or sending, by the MobileTerminal, Node or Entity, a message to the Home Gatekeeper/Home LocationDatabase, which notifies H.323 Home/Foreign Mobility Gatekeepers in apreselected area local to the Mobile Terminal/Node/Entity that theMobile TerminaVNode/Entity needs H.323 mobility services and notifying,by the H.323 Home/Foreign Mobility Gatekeepers, the MobileTerminal/Node/Entity of available H.323 Home/Foreign MobilityGatekeepers; registering, by the Mobile Terminal/Node/Entity, with aH.323 Home/Foreign Mobility Gatekeeper of the available H.323Home/Foreign Mobility Gatekeepers that support H.323 mobility servicesin a Location Area/Cell/Zone of the Mobile Terminal/Node/Entity; andproviding, for the Mobile Terminal/Node/Entity by the H.323 Home/ForeignMobility Gatekeeper with which the Mobile Terminal/Node/Entity isregistered, support for the H.323 communication that includes at leastone of: audio, video and data.

Registering with the H.323 Home/Foreign Mobility Gatekeeper may includesending registration information for the Mobile Terminal/Node/Entityusing a Base Station to Base Station Controller to Mobile SwitchingCenter to H.323 Home/Foreign Gatekeeper system in the case of thecellular wireless networking environment. In wireless/wire-lineLAN/wire-line environment, the H.323 mobile entity can register with theH.323 Home/Foreign Mobility GK via the wireless/wire-line LAN/wire-linewhere the GK may be connected to the packet network including thewireless/wire-line network. Registering with the at least one H.323Home/Foreign Mobility Gatekeeper may include sending registrationinformation for the Mobile Terminal/Node/Entity using awireless/wire-line Local Area Network to Router/Switch to H.323Home/Foreign Gatekeeper system. Where desired, registering may includethe steps of: broadcasting, multicasting, unicasting or sending, by theHome Gatekeeper, a Mobility Gatekeeper Advertisement (MGA) messageperiodically; broadcasting, multicasting, unicasting or sending aregistration request message (RRQ) to the Home Gatekeeper by the MobileTerminal/Node/Entity; and sending, by the Home Gatekeeper, aregistration confirmation/registration rejection (RCF/RRJ) to the MobileTerminal/Node/Entity.

Registering may also include the steps of: upon determining, by theMobile Terminal, Node or Entity, that a network point of attachment haschanged/a foreign zone has been entered, broadcasting, multicasting,unicasting or sending, by the Mobile Terminal, Node or Entity, aregistration request message (RRQ) to a Foreign/Visiting Gatekeeper;broadcasting, multicasting, unicasting or sending, by theForeign/Visiting Gatekeeper, a binding update message (BuRQ) to the HomeGatekeeper; broadcasting, multicasting, unicasting or sending, by theHome Gatekeeper, a binding update confirmation or rejection (BuCF/BuRJ)to the Foreign/Visiting Gatekeeper; broadcasting, multicasting,unicasting or sending, by the Foreign/Visiting Gatekeeper, the bindingupdate confirmation/rejection to the Mobile Terminal or Node/Entity.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:broadcasting, multicasting, unicasting or sending, by the HomeGatekeeper, a mobility unbinding message (UbRQ) to the VisitedGatekeeper; and broadcasting, multicasting, unicasting or sending, bythe Visited Gatekeeper, a mobility unbinding confirmation/rejection(UbCF/UbRJ) to the Home Gatekeeper. Where the MobileTerminal/Node/Entity has already visited another foreign zone regulatedby a Visited Gatekeeper, registering may include: broadcasting,multicasting, unicasting or sending, by the Mobile Terminal/Node/Entity,a registration request message (RRQ) to a Foreign/Visiting Gatekeeper;broadcasting, multicasting, unicasting or sending, by theForeign/Visiting Gatekeeper, a mobility unbinding update message (UbRQ)to the Visited Gatekeeper; broadcasting, multicasting, unicasting orsending, by the Visited Gatekeeper, a mobility unbindingconfirmation/rejection (UbCF/UbRJ) to the Foreign/Visiting Gatekeeper;broadcasting, multicasting, unicasting or sending, by theForeign/Visiting Gatekeeper, a provisional registration confirmation tothe Mobile Terminal, Node, or Terminal and broadcasting, multicasting,unicasting or sending, by the Foreign/Visiting Gatekeeper, a bindingupdate message (BuRQ) to the Home Gatekeeper; and broadcasting,multicasting, unicasting or sending, by the Home Gatekeeper, a bindingupdate confirmation or rejection (BuCF/BuRJ) to the Foreign/VisitingGatekeeper.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:broadcasting, multicasting, unicasting or sending, by the MobileTerminal, Node or Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper; broadcasting, multicasting, unicasting orsending, by the Visited Gatekeeper, a mobility unbinding confirmation orrejection (UbCF/UbRJ) to the Foreign/Visiting Gatekeeper; broadcasting,multicasting, unicasting or sending, by the Foreign/Visiting Gatekeeper,a provisional registration confirmation to the Mobile Terminal orNode/Terminal and broadcasting, multicasting, unicasting or sending, bythe Foreign/Visiting Gatekeeper, a binding update message (BuRQ) to theHome Gatekeeper; broadcasting, multicasting, unicasting or sending, bythe Home Gatekeeper, a binding update confirmation or rejection(BuCF/BuRJ) to the Foreign/Visiting Gatekeeper; broadcasting,multicasting, unicasting or sending, by the Home Gatekeeper, a mobilityunbinding update message (UbRQ) to the Visited Gatekeeper; andbroadcasting, multicasting, unicasting or sending, by the VisitedGatekeeper, a mobility unbinding confirmation/rejection (UbCF/UbRJ) tothe Home Gatekeeper.

Where desired, at least one Home or Foreign Gatekeeper may utilize acombined Home/Visitor Location Database. Also, where desired, aplurality of Home/Foreign Gatekeepers may each utilize an individualVisitor Location Database and share a Home Location Database.

Where the Mobile Terminal/Node/Entity is originally located in a FirstAdministrative Domain and is moving in a Second Administrative Domain,registering may include: broadcasting, multicasting, unicasting orsending a registration request message (RRQ), by the MobileTerminal/Node/Entity to the Foreign/Visiting Gatekeeper; broadcasting,multicasting, unicasting or sending, by the Foreign/Visiting Gatekeeper,a mobility unbinding (UbRQ) message to a Visited Gatekeeper;broadcasting, multicasting, unicasting or sending, by the VisitedGatekeeper, an unbinding confirmation or rejection (UbCF/UbRJ) to theVisiting/Foreign Gatekeeper; broadcasting, multicasting, unicasting orsending, by the Visiting Gatekeeper, a provisional registration messageto the Mobile Terminal/Node/Entity; broadcasting, multicasting,unicasting or sending, by the Foreign/Visiting Gatekeeper, a mobilitybinding message (BuRQ) to a Border Element of the Second AdministrativeDomain, which forwards the message to a Border Element of the FirstAdministrative Domain which then forwards the message to the HomeGatekeeper; broadcasting, multicasting, unicasting or sending, by theHome Gatekeeper, a mobility binding confirmation or rejection(BuCF/BuRJ) message to the Border Element of the First AdministrativeDomain, which forwards the message to the Border Element of the SecondAdministrative Domain, which forwards the message to the VisitingGatekeeper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one embodiment of an exemplary genericH.323 mobility architecture in accordance with the present invention.

FIG. 2 is a schematic showing an exemplary architecture of a zonecontaining cells in a wireless environment in accordance with thepresent invention.

FIG. 3 is a schematic diagram showing an exemplary architecture of azone containing wireless LANs and wire-line LAN or wire-line inaccordance with the present invention.

FIG. 4 is a flow chart of one embodiment of an H.323-based mobilityprotocol for real-time mobile multimedia communications and conferencingover packet-based networks in accordance with the present invention.

FIG. 5 is a flow chart showing one embodiment of steps for Databasinglocally in accordance with the present invention.

FIG. 6 is a flow chart showing one embodiment of steps for setting up amobile H.323-based call in accordance with the present invention.

FIG. 7 is a block diagram showing one embodiment of a computer-readablemedium having computer-executable steps for implementing, by a MobileTerminal Node/Entity, an H.323-based mobility protocol for real-timemobile multimedia communications and conferencing over packet-basednetworks in accordance with the present invention.

FIG. 8 is a block diagram showing one embodiment of an intra-zonemobility management system in accordance with the present invention.

FIG. 9 is a block diagram showing one embodiment of an inter-zonemobility management system in accordance with the present invention.

FIG. 10 is a block diagram showing one embodiment of location updatingduring registration for inter-zone communications in accordance with thepresent invention.

FIG. 11 is a block diagram showing one embodiment of location updatingduring registration for inter-domain communications in accordance withthe present invention when a mobile entity is in an administrativedomain other than its own.

FIG. 12 is a block diagram showing one embodiment of an architecture forZones, GateKeepers (GKs), and Home/Visitor Databases.

FIG. 13 is a block diagram showing one embodiment of a Centralized HomeLocation Database Architecture with GateKeepers(GKs) and Zones optimizedin accordance with the present invention.

FIG. 14 shows all fixed 1402 and mobile 1404 H.323 entities residingwithin a single zone.

FIGS. 15(a)-(b) show the call flows where a fixed entity has called amobile entity.

FIGS. 16(a)-(b) show the call flows where a mobile entity has called afixed entity.

FIGS. 17(a)-(b) show the call flows where a mobile entity has calledanother mobile entity.

FIG. 18 shows inter-zone communication for fixed and mobile entities.

FIGS. 19(a)-(b) depict call signaling between the fixed and the mobileentity located in two different zones: (a) Direct and (b) GK-routed.

FIG. 20 shows two mobile entities that are located in two separatezones. It is assumed that these entities are located in their respectivehome zones.

FIGS. 21(a)-(b) provide the call flow scenarios for the mobile-to-mobilecommunications while these entities are located in two separate zones:(a) Direct and (b) GK-routed.

FIGS. 22(a)-(b) depict a situation for the intra-zone handover where acall can be either directly routed or GK routed.

FIG. 23 shows the call flows that include the intra-zone handover from afixed entity with MC capability for a directly routed call to a mobileentity as the mobile moves from subnetwork 1 to subnetwork 2.

FIG. 24 shows the call signaling for the GK-routed handover from a fixedH.323 terminal to a mobile H.323 terminal where the GK has MCcapability.

FIGS. 25(a)-(b) show inter-zone handoffs that are needed for a (a)Directly Routed Call and a (b) GK-Routed Call because the mobile entitymoves out of the zone boundary.

FIG. 26 shows the call flows that includes the handover as the mobilemoves from (its home) zone 1 to visiting/foreign zone 2, i.e., callsignaling for inter-zone handovers: fixed entity with MC capability forthe directly routed Call.

FIG. 27 shows the inter-zone communications where the call is routed viaGK 1 that has the MC capability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides for extending the H.323 standard tosupport mobility in a multimedia communication system with services overpacket-based networks. The present H.323 standard is known to thoseskilled in the art and is hereby incorporated by reference. Theinvention supports extending H.323 to support mobility in a transportindependent way, create new H.323 messages and/or message elements thatneeded to support mobility, and facilitate interoperability forimplementation of H.323 mobility over specific networking environmentssuch as wireless/PSTN-IP. The invention provides for extension toexisting H.225.0 (H.323) messages to accommodate mobility. Messages areprovided to facilitate mobility binding as the mobile entity moves formone place to another. H.323 mobility service varies from traditionalservices such as cellular wireless/PSTN, and mobile IP, mobilityservices in that the IETF's mobile protocol may be modified to includean interworking function (IWF) to provide interoperability between themobile H.323 system and the wireless-PSTN mobile network.

When a mobile unit implementing H.323 uses a packet-based network, e.g.,the IP subnet, together with an H.323-based point of attachment (e.g.,network point of attachment, zone, domain), the mobility information ismanaged via a gatekeeper. There may be a gatekeeper at the transmittingend and at the receiving end also. If necessary, the gatekeeper can alsoperform bandwidth management, address translation, maps LAN aliases toIP addresses, and sets up a real-time transport control protocol (RTCP)for exchanging status information between the transmitting end and thereceiving end. A H.245 control channel is set up to provide controlfunctions such as, for example, opening and closing data channels.

The functional requirements of H.323 mobility are primarily descried atthe H.323 application level as:

Terminal Mobility: A fixed or mobile H.323 terminal must be able toreach an H.323 mobile user and vice versa. Conversations are providedeven when the mobile terminal moves from one place to another with adifferent point of attachment or network address. Where desired,communications are also provided among the H.323 mobile users.Intra-zone, inter-zone (intra-domain) and/or inter-domain handoff issupported. Handoff between intra-zone, inter-zone (intra-domain) and orinter-domain users is supported.

User Mobility: An H.323 user maintains the same identity and may receivethe same or, where desired, different services even when the user moves.Service providers may be switched with the user maintaining the sameidentity.

Mobility Management: The H.323 mobility management is supported toprovide registration, call establishment, roaming and handoff.

QoS Support: QoS service is maintained during intra-zone, inter-zone(intra-domain) and/or inter-domain roaming for the H.323 user.

Authentication and Security: Authentication and security mechanisms areprovided in support of H.323 mobility.

Typically, a gatekeeper (GK) manages a zone. A zone is generally acollection of H.323 entities such as terminals, gateways (GWs) orinterworking functions (IWFs), multiple controllers (MCs). Each H.323entity has a unique network point of attachment or address, and eachzone may contain many network points of attachment, subnets, oraddresses under the management of a GK. For example, a zone many havemultiple networks in the case of an IP, ATM, or other network. If a useror terminal moves within a zone, its network attachment or subnetworkaddress may also change.

A domain may consist of a single or of multiple zones. Thus, H.323mobility is addressed in terms of zones and domains as well. If an H.323user, entity or terminal crosses a zone boundary, such a change may betermed as a change of H.323 point of attachment because an H.323gatekeeper manages the registration of all H.323 entities in a givenzone. In addition, H.323 services are ensured during the call andbetween calls while users or terminals move from place to place.

Other terminology used herein is:

User mobility: the ability for a user to maintain the same user identityon different terminals or terminal types.

Terminal mobility: the ability for a terminal to changes location,network point of attachment, and H.323 point of attachment and still beable to communicate.

Discrete terminal mobility or roaming: the ability for a terminal tomake discrete changes of physical location, i.e., to change locationwhile no media streams are active.

Continuous terminal mobility or handover: the ability for a terminal tochange location while media streams are active. Such a change may beseamless, i.e., without loss of data, or alternatively, may not beseamless, i.e., wherein some media stream data is lost.

Service mobility: the ability for a user to obtain a particular serviceindependent of user and terminal mobility, i.e., wherein a foreignnetwork has the means to obtain the parameters required for the service.

Network Point of Attachment: the attachment or address, e.g., an IPaddress, of an H.323 entity, e.g., terminals, MCUs, MCs, and/or GWs, toa network. Similarly, the network point of attachment for ATM and othernetwork can also be defined. Each H.323 entity has at least one networkaddress which uniquely identifies the H.323 entity on the network. Theaddress is specific to the network environment in which the endpoint islocated. Different network environments may have different networkaddress formats. H.323 permits an endpoint to use different networkaddresses for different channels within the same call.

H.323 Point of Attachment: the gatekeeper with which an H.323 terminal,GW (IWF), MC, or MCU is Databased.

Mobile Entity: the H.323 entity that changes its point of attachment(network and/or H.323 point of attachment) from one attachment toanother. A mobile entity can continue to communicate with other H.323entities at any location as it moves from place to place.

Home GK: a gatekeeper in the mobile entity's home zone which performsthe necessary management functions for departed mobile entities andmaintains current location information for each. Any H.323 GK thatprovides the support for H.323 mobile entities can act as a home GK.

Home Network: the network in the mobile entity's home network and thenetwork which has been declared by the mobile entity as its homenetwork, e.g., an IP subnetwork in the home zone declared as a homenetwork by a mobile entity.

Home Network Address: the address of the network point of attachment inthe home network of a mobile entity, e.g., IP address (RAS transportaddress) in a home IP subnetwork. If the transport address contains thenetwork address in addition to the TSAP, the home transport address willalso contain the home network address.

Foreign GK: a gatekeeper on a mobile entity's visited- or visiting-zonewhich cooperates with the home GK to have the information related to themobile entity while it is away from its home zone. Any H.323 GK thatprovides the support for H.323 mobile entities can act as a foreign GK.

Foreign Network: the network in the mobile entity's foreign zone wherethe said network has been declared by the mobile entity as its foreignnetwork, e.g., an IP subnetwork in a foreign zone of a mobile entity.

Care-of Network Address: the address of the network point of attachmentin a foreign network of a mobile entity, e.g., IP address (RAS transportaddress) in a foreign IP subnetwork. If the transport address containsthe network address in addition to the TSAP, the care-of transportaddress will also contain the care-of network address.

Visiting GK: a foreign GK that the mobile entity is presently visiting,i.e., the mobile entity is currently residing within a foreign zone thatis managed by a foreign GK.

Visited GK: the foreign GK that had been visited by the mobile entitypreviously.

Target GK: the foreign GK that the mobile entity intends to visit.

Target Network: the target network that the mobile entity intends tovisit.

Mobile GK: either a home GK or a foreign GK.

Home Zone: a zone that is managed by a home GK of a mobile entity.

Foreign Zone: a zone managed by a foreign GK.

Visiting Zone: a zone other than a mobile entity's home zone in whichthe mobile entity is currently residing, i.e., a foreign zone in whichthe mobile entity is presently visiting.

Visited Zone: a zone other than a mobile entity's home zone that themobile entity has visited previously, i.e., the foreign zone which hadbeen visited by the mobile entity previously.

Target Zone: a zone other than a mobile entity's home zone that themobile entity intends to visit.

Visiting Entity: a mobile entity that is residing in a visiting zonemanaged by a visiting GK.

Visiting Terminal: a mobile H.323 terminal that is residing in avisiting zone managed by a visiting GK.

Visiting User: a mobile H.323 terminal that is residing in a visitingzone managed by a visiting GK.

Visitor List: the list of mobile entities currently visiting a foreignzone.

GK Advertisement for Mobility Services: foreign gatekeepers advertisetheir presence by using a special message to provide services for mobileentities.

Care-of Address: the terminal address of the point of attachment, e.g.,care-of network address of mobile entity or care-of address of a foreignGK where a mobile entity is residing. There are two different types ofcare-of address: a foreign GK care-of address with which a mobile entityis Databased; a care-of network address which the mobile entity hasassociated with one of its own network interfaces, e.g., a temporary IPaddress of the visitor may be acquired dynamically using the DynamicHost Configuration Protocol (DHCP).

Location Area: a location area may constitute a cell or a certain groupof cells in a given geographical area that resides within a zone.

Administrative Domain: An administrative domain is a collection of H.323entities administered by one administrative entity and may contain oneor more gatekeepers (that is one or more zones). It may also contain oneor more border elements for communications between the domains. Likezone, an administrative domain can also be termed as home or foreign(visited, visiting, or target) domain.

Mobile H.323 (Mobile H.323 Protocol): the extended and existingH.323/H.225.0/H.245 messages that are used to support mobility in H.323are termed as mobile H.323 protocol or simply as mobile H.323.

Clearly, H.323 mobility provides two kinds of changes in point ofattachment: changing Network Point of Attachment in H.323 to H.323 calls(it can also be termed as a part of change in H.323 point ofattachment), and changing H.323 Point of Attachment (e.g., change inzone or domain). Broadly speaking, both kinds of change in attachmentcan be termed as change in H.323 point of attachment. The change ofattachment can also occur during calls, i.e., handover, and betweencalls, e.g., roaming. A change in point of attachment, e.g., a change inIP address or a change in zone/domain boundary, may result in handoverduring the call.

FIG. 1 shows a generic configuration of H.323 mobility architecture. Itshows that H.323 mobile entity 1 102 resides within a zone 1(home/foreign) 104 where zone 1 is controlled by gatekeeper 1(home/foreign) 106. For an H.323 mobile entity that has designated thiszone as its designated home zone, the gatekeeper of this zone will alsobe its home gatekeeper. An H.323 mobile entity Gatekeeper 1 may keep theinformation related to mobile entities that have designated thisgatekeeper (and thereby the zone) as their home gatekeeper 1 (andthereby the home zone) to a database known as home location database 1108. However, if the H.323 mobile entity is a visitor from another zoneor domain, then is this gatekeeper and zone will be its foreigngatekeeper and foreign zone. Again, as defined earlier, a foreigngatekeeper/zone can also be visited, visiting, or target gatekeeper/zonedepending on the criteria whether or not the mobile entity visited,visiting, or target to visit the gatekeeper/zone. If it is so,gatekeeper 1 designated as the foreign gatekeeper may keep theinformation related to the foreign mobile entity to a database knownvisitor location database 1. It may be noted that home or visitorlocation database can be implemented combining both functions togetheror they can be two independent entities depending on the implementation.A foreign gatekeeper may have to contact foreign mobile entity's homegatekeeper and/or home location database to know the detail about themobile entity (e.g., authentication, authorization, profileverification, service criteria, etc.), and a protocol is needed forcommunications between the foreign GK/visitor location database and thehome GK/home location database. Similar is the case for mobile entity 2110 which is in home/foreign zone 3 112. Each zone has to deal with eachmobile entity in accordance to the criteria as describe earlier. It isinteresting to note that there can be a single or multiple home/visitorlocation databases depending on the need of the design criteria.

In FIG. 2, it is shown that a zone may also contain cells in wirelessnetworking environment. A cell may vary in size depending on networkingdesign criteria. For example, the cell size of the existing cellularnetwork can be termed as macro-cell, whereas the smaller cells,especially in the indoor environment, can be termed as micro- orpico-cell. Within a cell, there can base station (BS), base stationcontroller (BSC), and/or mobile switching center (MSC)). An MSC maycontain router (e.g., IP router) or switch (e.g., ATM switch, FR switch,etc.). An H.323 mobile entity residing in a cell will be communicatingwith a base station (BS) using the wireless link. In turn, the basestation will be communicating to a base station controller, and a basestation to an mobile switching center. A gatekeeper may be connected toan MSC while a gatekeeper (home/foreign) will communicate with thehome/visitor location database as appropriate as described in FIG. 1.FIG. 2 is a block diagram showing one embodiment of a mobile H.323entity 202 operating in a home/foreign zone 214 and communicating usinga local Base Station (BS) 204 that communicates with a Base StationController (BSC) 206 in accordance with the present invention. The BSC206 is one of a plurality of BSCs operating in the home/foreign zone214, and the BSC 206 forwards the communication from the mobile H.323entity to a Mobile Switching Center (MSC) 208 in the home/foreign zone214. There may be a plurality of MSCs in the home/foreign zone 214. TheMSC 208 then forwards the mobile H.323 entity's communication to thehome/foreign GK 210 with which the mobile H.323 entity 202 isregistered. Typically, the home/foreign GK 210 has a home/visitorlocation database 212 for storing location information for mobile H.323entities which are registered for the home/foreign zone 214.

In FIG. 3, another architecture of a zone is shown where a zone containswireless LANs, wire-line LANs, wire-lines, etc. In the case of wirelessLANs (e.g., Ethernet, Token Ring, ATM, LAN/Hub, etc.), the mobile entitymay be directly communicating to a router or switch via wireless devicesconnected to the LAN. In the case of end-to-end wire-line network, themobile entity is directly connected to the network via wire. Like FIG.2, the gatekeeper (home/foreign) can communicate to the home/visitorlocation database as appropriate as described in FIGS. 1 and 2.

FIG. 3 is a block diagram showing one embodiment of mobile H.323entities 302, 304 arranged to communicate with a wireless LAN 308, 310and a mobile H.323 entity 306 that is coupled to a wire-line LAN 312 inaccordance with the present invention. The wireless LANs 308, 310 andthe wire-line LAN 312 are coupled to their respective Router/Switches(R/Sws) 314, 316, which communicate with the home/foreign GK 318 for thehome/foreign zone 322 that encompasses the mobile region for the mobileentities.

FIGS. 1, 2, and 3 show clearly that a zone/domain may have a variety ofarchitectures and architectural entities over which H.323 mobilityprotocol can be applied transparently. However, if an H.323 mobileentity moves, the network point of attachment also changes that also maycause to change in zone and/or domain. For example, changing a networkpoint of attachment in H.323 to H.323 cells may be done during a call,i.e., a handover, and may be intra-zone, inter-zone, or inter-domain;changing a network point of attachment in H.323 to H.323 cells may alsobe accomplished between calls, e.g., roaming, and may also beintra-zone, inter-zone, or inter-domain. Changing an H.323 point ofattachment may occur during a call, i.e., handover, and may beintra-zone, inter-zone, or inter-domain; similarly, changing an H.323point of attachment may occur between calls, e.g., roaming, and may alsobe intra-zone, inter-zone, or inter-domain.

Mobile H.323 solves the mobility problems at the middleware/applicationlayer. Thus, solutions for the mobile H.323 complement the mobilitysolutions provided in the lower packet-based transport network, e.g.,mobile IP developed by the IETF for the IP transport network and aninterworking scheme is defined between the packet-based mobile H.323system and the existing circuit-switched-based wireless-PSTN networks,e.g., ANSI-41 and GSM MAP of Public Land Mobile Network (PLMN) using theinterworking function (IWF) or gateway (GW).

Roaming and handover handling, which are not provided form by thecurrent version of H.323, are important mechanisms to support mobility.In order to support mobility, H.323 requires extension for integrationof roaming and handover operations along with registration (pre-callsetup), location update, call establishment, and call teardown. Duringhandover, a continuity of each medium stream needs to be provided whilea terminal changes its location. For example, in a wireless LAN orcellular network, an H.323 mobile entity may be available in more thanone link at a time (i.e., within wireless transmitter range of networkdevices on more than one separate link), and simultaneous connectionsmay co-exist for a brief period of time until the handover is completed.The resources to the new location will be allocated, and the resourcesto the old location will be released.

In using H.323, an H.323 entity registers to a Gatekeeper for admissionto the H.323 system using the registration, admission, and status (RAS)signaling messages. The Gatekeeper, which is optional in an H.323system, provides call control services to the H.323 endpoints. More thanone Gatekeeper may be present and communicate with each other in anunspecified fashion. The Gatekeeper is logically separate from theendpoints; however, its physical implementation may coexist with aterminal MCU, GW or IWF, MC, or other non-H.323 network device.

When present in a system, a Gatekeeper provides many services: AddressTranslation, Admission Control, Bandwidth Control, and Zone Management.The Gatekeeper may also perform other optional functions such as: CallControl Signaling, Call Authorization, Bandwidth Management, CallManagement, Bandwidth reservation for terminals not capable of their ownbandwidth reservation, Directory Services and the like. Thus, aGatekeeper becomes the functional entity to manage mobility in H.323that will enable mobile H.323-based multimedia telephony over thepacket-based networks for both connectionless and connection-orientednetworking environment.

A zone may have many subnetworks controlled by a single gatekeeper. If aterminal or user moves within a zone, its network point of attachment,e.g., IP subnetwork (RAS transport address), may change, although itwill remain under the control of the same Gatekeeper. The mobile entityneeds to register with the Gatekeeper to update its new network point ofattachment. Accordingly, the new resources may also need to be allocatedconsidering the new network point of attachment while the resourcesallocated, if any, to the old attachment, need to be released.

However, communications between the Gatekeepers will be requiredparticularly to update the mobile's location when a terminal or usercrosses the zone boundary, involving inter-zone communications betweenthe desired functional entities. If needed, resources may also need tobe allocated to the new point of attachment of the mobile entity, andthe resources to the old point of attachment may be required to be takenoff. In order to facilitate such changes, the terminology home GK,foreign GK, home zone, foreign zone, etc. is utilized. A home GK is agatekeeper with whom an H.323 entity registers and designates as itshome GK. A home zone is a zone which is managed by an H.323 entity'shome GK. A foreign GK is a gatekeeper with whom an H.323 entityregisters after moving from its home zone. A foreign zone is a zonewhich an H.323 entity's home GK does not manage.

A foreign zone in which an H.323 entity is residing presently may alsobe termed as a visiting zone and, the foreign GK may also be termed avisiting GK. A foreign zone in which an H.323 mobile entity had beenresiding previously may also be termed a visited zone and the foreign GKmay also be termed as the visited GK. A terminal or user may be termed avisiting terminal or user when the H.323 entity remains in the foreignzone.

An H.323 mobile entity needs to register with a mobile GK that willserve as its home GK. The home GK becomes the controlling entity as themobile entity moves from place to place. If needed, the mobile entitymay also determine which GK will become its home GK. Once the mobileentity determines which GK will become its home GK, the mobile entitythen registers with the selected GK.

A mobile GK typically advertises periodically its availability toprovide mobility services for the visiting mobile entities in its zone.The visiting mobile entities will register with the mobile (foreign) GKupon receiving the advertisement message. While in a foreign zone, themobile entity may also seek a foreign GK using a gatekeeper discoverymessage. In any case, the mobile terminal registers with the foreign GKupon crossing the home zone boundary. The foreign GK then communicateswith the H.323's home GK for registration and location updateinformation.

An H.323 mobile entity designates a GK as its home GK throughregistration. The home GK is the central functional entity that managesmobility and authentication for the mobile entity. The home transportaddress (RS, Call Signaling) of the home subnetwork of the home zone ofthe mobile entity is provided to the home GK during registration. As themobile entity moves form one place to another, the registration of themobile entity's current information is exchanged with its home GK.Registration is required before any call is attempted.

An option, similar to the mobile IP protocol, may be provided to keepthe home transport address fixed for a mobile entity. That is, an H.323entity may always send a call to another a mobile entity's fixed hometransport address in the home zone managed by the mobile entity's homeGK, and the home GK then establishes the call to the mobile entity'spresent care-of address (i.e., a home GK-routed call). In this way, amobile entity's care-of address will not be known to the calling partyor entity, and a mobile entity can hide its location. However, a callmay be established directly to the care-of transport address of themobile entity if mobile entity's address is known. This can be done ifthe mobile entity's address is priori known to the calling entity or ifthe policy is such that the home gatekeeper is allowed to let theaddress of the called mobile entity be known to the calling entity. Inthis way the home gatekeeper will let the calling entity know thecare-of address of the called mobile entity, and the calling entity canthen directly establish the call to mobile's care-of address.

A mobile GK advertises its availability for mobility services, and amobile entity may solicit the availability of the mobile GK as themobile GK moves from one zone to another.

When needed, a paging message may be sent for the location discovery ofa mobile entity. During location updating after receiving the pagingmessage, where a mobile entity has not yet been registered, it goesthrough a registration process.

A gatekeeper manages the H.323 mobile entities. Each mobile H.323belongs to a home GK where it registers for subscription of mobilityservices. The home GK needs to keep track of a mobile H.323 entity'slocation along with other information (e.g., user profiles, accountinginformation, etc.) a it moves from one place to another. A user profilemay contain call-related information (such as call forwarding, callbarring, and the like), close user group (CUG) information, roamingrestrictions, supplementary services, subscription categories, etc. Agatekeeper may contain one or more subnetworks that constitute a zone.In some instances, each subnetwork may be an access network or locationarea/Cell/Zone (e.g., wireless LAN, wireless access unit of the cellularnetwork, etc.), and each zone may contain one or many access networks orlocation areas/Cell/Zone. A foreign GK keeps track of visiting H.323entities that are operating in the specific foreign GK's serving zone.Originally, the location of an H.323 entity is known to its home GK andthe foreign GK must communicate with the visiting entity's home GK. Theforeign GK must inform the visiting entity's home GK when the visitingH.323 entity registers with it, and the home GK updates its records toreflect that the mobile subscriber is now located a the new location.

An H.323 mobile entity may also move from one foreign zone to anotherforeign zone. During the communication process, the home GK may alsoneed to communicate with the visited GK about the mobile H.323 entity orsubscriber in addition to the visiting GK because the home GK keepscomplete information about its mobile subscribers. The home GK and theforeign GK may also exchange security information (e.g., H.235) toprovide authentication, privacy, and integrity. If needed, the H.235security mechanisms may be extended to include special features for themobile environment. Such features may include random numbers used forauthentication (e.g., RAND), ciphering a key sequence number (e.g.,CKSN), and security parameters in response to an authentication request(e.g., SRES). In addition, a home GK may keep the equipment identityregister (EIR) that contains information the H.323 mobile subscriberequipment. The EIR may contain the identification of the manufacturer ofthe mobile subscriber equipment (e.g., the International MobileEquipment Identity IMEI)), conformance testing information, and theidentifier of the factory that assembled the H.323 mobile equipment.Moreover, the International Mobile Subscriber Identity (IMSI) and theTemporary Mobile Subscriber Identity (TMSI) may also be used by theH.323 mobile subscribers as appropriate. These special mobile subscriberidentities may also be stored in a home GK at the time of registrationby the mobile users. A mobile subscriber determines whether to use theIMSI or TMSI. The IMEI, IMSI, and TMSI numbers may be considered asanother kind of H.323 alias addresses. However, the IMEI is primarilyhelpful for the terminal mobility, while the IMSI and TMSI are utilizedmore in describing the user mobility.

H.323 mobility services may be described with respect to the highermiddleware/application layer in a transport independent manner. Atpresent, H.323 provides mechanisms to discover a GK by an H.323 entityusing Gatekeeper Request (GRQ), Gatekeeper Confirmation (GCF), andGatekeeper Reject (GRJ) messages. These messages are extended in thepresent invention to manage the mobile environment.

If an H.323 mobile entity desires to receive mobility services, such amobile entity must first determine its home GK of its home zone thatwill act as the central entity to manage its mobility. The GRQ/GCF/RJmessage may be extended to determine the home GK. Once the home GK isknown, the mobile entity may then use registration messages to registerwith the home GK. Again, the registration messages of H.323 as itpresently exists may be extended to the mobile environment. Uponcrossing a home zone boundary, the mobile H.323 entity must re-registerwith the foreign GK. A H.323 gatekeeper that provides mobility servicesadvertises its availability using a Mobility Gatekeeper Advertisement(MGA) message periodically with a multicast address. Upon receiving theMGA message, the mobile entity may detect a mobile GK that can supportservices related to mobility. If necessary, the mobile entity may alsosend the extended GRQ message to determine the mobile GK in the foreignzone. However, it is preferable to determine the mobile GK with the helpof the MGA message. An H.323 mobile entity may use the extendedregistration messages to register with the mobile GK when it determinesthe mobile GK with which it needs to register in a foreign zone. Amobile entity can detect that it has crossed a zone boundary into aforeign zone through examining MGA messages.

Typically, the MGA message informs the mobile entities about the specialfeatures of the advertisement and typically includes the followingfields:

RequestSeqNum: a monotonically increasing number unique to the sender.It is returned by the receiver in any messages associated with aspecific message.

AdvertisedTimeToLive: duration of the validity of the registration withthe mobile GK, typically in seconds. After this time elapses, thegatekeeper may consider the registration no longer current.

NeedToRegisterWithGK: set to TRUE to indicate that the mobile entitymust register with this foreign gatekeeper before sending other RASrequests.

BusyForeignGK: set to TRUE to indicate that the foreign gatekeeper isbusy. HomeGKIdentifier: is an OPTIONAL field that is included toidentify the home gatekeeper. If it is supplied, it is included infuture RAS messages sent to the home gatekeeper. This gatekeeper acts asthe central entity to manage the mobility of the mobile entity that willdesignate this gatekeeper as its home gatekeeper.

ForeignGK: an OPTIONAL field that is used to indicate the gatekeeperthat works as a foreign gatekeeper when the mobile entity enters intothe zone controlled by this gatekeeper. The structure of the foreigngatekeeper includes:

ForeignRASAddress: the transport address used for RAS signaling. Thisaddress is used as the care-of gatekeeper address for the mobile entity.

ForeignGKIdentifier: optionally included to identify the foreigngatekeeper. If it is supplied, it is included in future RAS messagessent to the foreign gatekeeper.

ZoneRange: a list of subnetworks covered by a mobile (home/foreign) GKin a given zone.

NonStandardData: carries information not defined (for example,proprietary data).

A GK may act as both a home GK and a foreign GK for mobile users. Thesame GK will also act as a “normal” GK for fixed users that are notdesignated as mobile users. In such a situation, typically both the homeGK and the foreign GK will have the same gatekeeper identifier and thesame RAS address. The ZoneRange is the same for both the home GK and theforeign GK because there is only one GK in a given zone. Home GKs do nothave to advertise the care-of address, but still must broadcast,multicast, or unicast MGA advertisements so that mobile entities willknow when they have returned to their home zone. The mobile entityupdates its location to its home GK when it returns to its home zone. Itshould be noted that a foreign GK may not indicate that it is busyunless it declares that it is a foreign GK. Also, it should be notedthat a foreign GK must continue sending advertisements out, even thoughit is too busy to provide service to new mobile entities. Otherwise, theforeign GK's current customers may think that the foreign GK hascrashed, and move away unnecessarily. The mobile GK will generallyincrement the sequence number by one for each successive advertisement.

Extensions to the GRQ messages allow an alternative means to discoverthe mobile GK (home or foreign) by a mobile entity. If the MGA messageis not received within a certain period of time, the mobile entity mayprefer to use these extended messages to discover the mobile GK. Theremay be other reasons such as use of the same method for discovering theGK for both fixed and mobile entities, to use the GRQ messages todiscover the mobile GK.

A mobile entity can find the mobile GK that will serve as its home GK inits home/zone in one of two ways: Manually or Dynamically using the GKdiscovery messages (GRQ/GCF/GRJ). Similarly, a mobile entity may alsoseek to discover dynamically which GK it needs to register with once itdetermines that it is in a foreign zone, assuming that it has notreceived the MGA message from the mobile GK. The GRQ/GCF/GRJ messageshave been extended to cover the mobile user as described below.

The main purpose of the GRQ message is to discover a GK for a fixed ormobile entity. Thus, the information related to the visited or target GKis not required. However, new OPTIONAL alias addresses like IMEI, IMSI,and TMSI need to be included. The GRQ message needs to be extended asfollows:

HomeZone: set to TRUE to indicate that a mobile entity is seeking aregistration in a home zone.

ForeignZone: set to TRUE to indicate that a mobile entity is seeking aregistration in a foreign zone.

HomeGK: an OPTIONAL field to indicate the gatekeeper that acts as themobile entity's home gatekeeper when the mobile entity enters into aforeign zone. The information related to the HomeGK is provided if theForeignZone field is set to TRUE.

The structure of the home GK contains:

HomeRASAddress: the transport address used for RAS signaling. Thisaddress is used as the home RAS transport address for the mobile entityin its home zone.

HomeCallSignalAddress: the transport address used for call signaling.This address is used as the home call signaling transport address forthe mobile entity in its home zone.

HomeGKIdentifier: an OPTIONAL field that identifies the home gatekeeper.If it is supplied, it is included in future RAS messages sent to thehome gatekeeper.

EndpointAlias: additional OPTIONAL International Mobile EquipmentIdentify (IMEI), International Mobile Subscriber Identity (IMSI) andTemporary Mobile Subscriber Identity (TMSI) alias addresses are includedherein.

It is important to note that if the HomeZone is set to TRUE, theForeignZone may not be set to TRUE and vice versa. If both the HomeZoneand the ForeignZone are set to FALSE, or none of these extended messagefields are used, it is the fixed H.323 entity that is seeking todiscover the GK. If the HomeZone is set to TRUE, no information relatedto the HomeGK field is supplied. Thus, with respect to the present H.323system, the RASAddress field of the GRQ message becomes the home RAStransport address (HomeRASAddress) of the mobile entity. Similarly, thegatekeeperIndentifier field, if used to identify the gatekeeper, becomesthe home gatekeeper (HomeGKIdentifier) of the mobile entity. Thetransport address provided in the alternateEndpoints field of thepresent H.323 becomes the alternate home transport address(EndpointAlias) of the mobile entity.

If the ForeignZone is set to TRUE, the information related to the HomeGKfield may also be supplied. The information related to the home GK maybe used to serve many purposes. For example, the serving mobile GK(visiting GK) may be able to differentiate services based on theinformation of the home GK, if needed. It can be seen that theRASAddress of the GRQ message supplied by the mobile entity becomes itscare-of transport address once it indicates that it is in a foreignzone. However, it is important to note that the mobile entity mustacquire the care-of transport address before seeking a care-of (foreign)GK using the GRQ message after moving to the foreign zone (e.g., atemporary IP address of the visitor (mobile entity in a foreign zone)may be acquired dynamically by such means as the DHCP in the respectivesubnet. Similarly, the OPTIONAL gatekeeperIndentifier field, if knownprior to the mobile entity, also provides the indication as mobileentity's care-of gatekeeper in the foreign zone. The transport addressprovided in the OPTIONAL alternateEndpoints field becomes the alternatecare-of transport address of the mobile entity in the foreign zone.Moreover, additional information about the homeRASAddress and thehomeCallSignalingAddress transport address will be supplied by themobile entity for indicating to its mobile GK that these addresses arein its home zone. The mobile entity will supply its home gatekeeperidentification in the homeGKIdentifier field.

The GCF message is extended as follows:

HomeZone: set to TRUE to indicate that a mobile entity is seeking aregistration in a home zone.

ForeignZone: set to TRUE to indicate that a mobile entity is seeking aregistration in a foreign zone.

AdvertisedTimeToLive: an OPTIONAL field. However, if the ForeignZonefield is set to TRUE, this field shall be used. This field provides theduration of the validity of the registration with the mobile GK,typically in seconds. After this time, the gatekeeper may consider thatthe registration is no longer current.

If HomeZone is set to TRUE, ForeignZone cannot be set to TRUE and viceversa. If both HomeZone and ForeignZone are set to FALSE or none of theextended message fields are used, it is the fixed H.323 entity's GK thathas been confirmed.

If the HomeZone field of the GCF message is set to TRUE, the RASAddressfield of the GCF message becomes the transport address of the home GK ofthe mobile entity. Similarly, the gatekeeperidentifier field, if used toidentify the gatekeeper, becomes the identity of the home GK of themobile entity. The transport address and gatekeeper identifier providedin the alternateGatekeeper field becomes the transport address andgatekeeper identifier of the alternate home GK of the mobile entity. Ifthe ForeignZone field is set to TRUE, the RASAddress field of the GCFmessage becomes the care-of transport address of the foreign GK of theforeign GK of the mobile entity. Similarly the gatekeeper/Indentifierfield, if used to identify the gatekeeper, becomes the identify of theforeign G of the mobile entity. The transport address and gatekeeperidentifier provided in the alternateGatekeeper field becomes thealternate transport address and gatekeeper identifier of the alternatecare-of foreign GK of the mobile entity.

The GRJ message is extended as follows:

Home Zone: set to TRUE to indicate that a mobile entity is seeking aregistration in a home zone.

ForeignZone:set to TRUE to indicate that a mobile entity is seeking aregistration in a foreign zone.

HomeGKNotServe: this optional field can be used if the foreign field isset to TRUE. The foreign GK with which a mobile entity is trying toregister with may deny registration if it does not want to servevisitors (mobile entities) of that particular zone. If the HomeZonefield is set to true, the ForeignZone cannot be set to true and viceversa. If both the HomeZone and ForeignZone fields are set to FALSE, ornone of these extended message fields are used, it is the fixed H.323entity's request for seeking a GK that has been rejected. If theHomeZone field is set to TRUE, the gatekeeperIdentifier field of the GRJmessage, if used to identify the gatekeeper, indicates the GK that themobile entity wanted to register with as its foreign GK. The informationprovided in the optional altGKinfo field indicates the mobile entityneeds to try an alternative GK provided in the list to serve as itsforeign GK.

FIG. 4 is a flow chart of one embodiment of an H.323-based mobilityprotocol for real-time mobile multimedia communications and conferencingover packet-based networks in accordance with the present invention. Aplurality of H.323 mobility gatekeepers provide notification of H.323mobility services availability by periodicallybroadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisementwith a multicast/unicast address. The protocol typically includes thesteps of: upon becoming mobile and initiating an H.323 communicationthat includes at least one of: audio, video and data, by the MobileTerminal/Node/Entity, with respect to notification 402, one of:providing, by at least one of a plurality of available H.323Home/Foreign Mobility Gatekeepers, notification of H.323 mobilityservices availability by periodicallybroadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisementwith a multicast/unicast address; and where the MobileTerminal/Node/Entity lacks notification of H.323 mobility servicesavailability, broadcasting/multicasting/unicasting sending, by theMobile Terminal/Node/Entity, a message to the Home Gatekeeper/HomeLocation Database, which notifies H.323 Home/Foreign MobilityGatekeepers in a preselected area local to the MobileTerminal/Node/Entity that the Mobile Terminal/Node/Entity needs H.323mobility services and notifying, by the H.323 Home/Foreign MobilityGatekeepers, the Mobile Terminal/Node/Entity of available H.323Home/Foreign Mobility Gatekeepers; registering 404, by the MobileTerminal/Node/Entity, with a H.323 Home/Foreign Mobility Gatekeeper ofthe available H.323 Home/Foreign Mobility Gatekeepers that support H.323mobility services in a Location Area/Cell/Zone of the MobileTerminal/Node/Entity; and providing 406, for the MobileTerminal/Node/Entity by the H.323 Home/Foreign Mobility Gatekeeper withwhich the Mobile Terminal/Node/Entity is registered, support for theH.323 communication that includes at least one of: audio, video anddata.

Registering with the H.323 Home/Foreign Mobility Gatekeeper may includesending registration information for the Mobile Terminal/Node/Entityusing a Base Station to Base Station Controller to Mobile SwitchingCenter to H.323 Home/Foreign Gatekeeper system. Alternatively,registering with the at least one H.323 Home/Foreign Mobility Gatekeepermay include sending registration information for the MobileTerminal/Node/Entity using a wireless/wire-line Local Area Network toRouter/Switch to H.323 Home/Foreign Gatekeeper system.

As shown in FIG. 5, in one embodiment, registering may include the stepsof: broadcasting/multicasting/unicasting sending 502, by the HomeGatekeeper, a Mobility Gatekeeper Advertisement (MGA) messageperiodically; broadcasting/multicasting/unicasting/sending 504 aregistration request message (RRQ) to the Home Gatekeeper by the MobileTerminal/Node/Entity; and broadcasting/multicasting/unicasting sending506, by the Home Gatekeeper, a registration confirmation/registrationrejection (RCF/RRJ) to the Mobile Terminal/Node/Entity.

As shown in FIG. 6, in another embodiment, registering may include thesteps of: upon determining, by the Mobile Terminal/Node/Entity, that anetwork point of attachment has changed/a foreign zone has been entered,broadcasting/multicasting/unicasting/sending 602, by the MobileTerminal/Node/Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper;broadcasting/multicasting/unicasting/sending 604, by theForeign/Visiting Gatekeeper, a binding update message (BuRQ) to the HomeGatekeeper; broadcasting/multicasting/unicasting/sending 606, by theHome Gatekeeper, a binding update confirmation/rejection (BuCF/BuRJ) tothe Foreign/Visiting Gatekeeper;broadcasting/multicasting/unicasting/sending 608, by theForeign/Visiting Gatekeeper, the binding update confirmation/rejectionto the Mobile Terminal/Node/Entity.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, amobility unbinding message (UbRQ) to the Visited Gatekeeper; andbroadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the HomeGatekeeper.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:broadcasting/multicasting/unicasting/sending, by the MobileTerminal/Node/Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a mobility unbinding update message (UbRQ) to the VisitedGatekeeper; broadcasting/multicasting/unicasting/sending, by the VisitedGatekeeper, a mobility unbinding confirmation/rejection (UbCF/UbRJ) tothe Foreign/Visiting Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a provisional registration confirmation to the MobileTerminal/Node/Terminal and broadcasting/multicasting/unicasting/sending,by the Foreign/Visiting Gatekeeper, a binding update message (BuRQ) tothe Home Gatekeeper; and broadcasting/multicasting/unicasting/sending,by the Home Gatekeeper, a binding update confirmation/rejection(BuCF/BuRJ) to the Foreign/Visiting Gatekeeper.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:

broadcasting/multicasting/unicasting/sending, by the MobileTerminal/Node/Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to theForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a provisional registration confirmation to the MobileTerminal/Node/Terminal and broadcasting/multicasting/unicasting/sending,by the Foreign/Visiting Gatekeeper, a binding update message (BuRQ) tothe Home Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, abinding update confirmation/rejection (BuCF/BuRJ) to theForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, amobility unbinding update message (UbRQ) to the Visited Gatekeeper; and

broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the HomeGatekeeper.

In one embodiment, at least one Home/Foreign Gatekeeper utilizes acombined Home/Visitor Location Database. In another embodiment, aplurality of Home/Foreign Gatekeepers each utilize an individual VisitorLocation Database and share a Home Location Database.

Where the Mobile Terminal/Node/Entity is originally located in a FirstAdministrative Domain and is moving in a Second Administrative Domain,registering may include:

broadcasting/multicasting/unicasting/sending a registration requestmessage (RRQ), by the Mobile Terminal/Node/Entity to theForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a mobility unbinding (UbRQ) message to a Visited Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,an unbinding confirmation/rejection (UbCF/UbRJ) to the Visiting/ForeignGatekeeper;

broadcasting/multicasting/unicasting/sending, by theVisiting-Gatekeeper, a provisional registration message to the MobileTerminal/Node/Entity; broadcasting/multicasting/unicasting/sending, bythe Foreign/Visiting Gatekeeper, a mobility binding message (BuRQ) to aBorder Element of the Second Administrative Domain, which forwards themessage to a Border Element of the First Administrative Domain whichthen forwards the message to the Home Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, amobility binding confirmation/rejection (BuCF/BuRJ) message to theBorder Element of the First Administrative Domain, which forwards themessage to the Border Element of the Second Administrative Domain, whichforwards the message to the Visiting Gatekeeper.

Where desired, an H.323 mobility gatekeeper may provide forauthentication of the mobile entities/users. Typical H.323 mobilityservices may include address translation, admissions control, bandwidthcontrol, and/or zone management.

A mobile entity needs to send (Registration ReQuest, RegistrationConFirmation, and Registration Reject (RRQ/RCF/RRJ) messages to its homeor foreign mobile GateKeeper (GK) for registration when the mobile GKhas been determined either by receiving the MGA message from the mobileGK or by sending extended GRQ messages. The following describes how amobile entity registers with the home or foreign GK while the entity isin a home/foreign zone.

In H.323, there are three kinds of registration messages: RRQ, RCF andRRJ. Since mobility introduces additional requirements, the registrationmessages are extended to satisfy all the additional requirements. Theregistration messages allow mobile entities to register with either ahome or a foreign GK. The extended registration request message allowsthe mobile entity to inform its home GK of its current care-of addressin a foreign zone, set forth how long the mobile entity desires to usethe care-of address, and indicate special features that may be availablefrom the foreign agent using the mobility binding update messages(BuRQ/BuCF, BuRJ). The foreign GK is considered a passive GK in theregistration procedure, and may agree to pass the request to the homeGK, and subsequently to pass the reply from the home GK back to themobile entity.

In H.323, each home is managed by a single GK and, the said GK is thesole agent entity to perform all functions specified in the standard.Accordingly, the said GK will be able to perform services for both fixedand mobile entities. That is, the same GK, if needed, may also performthe functions of the home GK and foreign GK along with the services ofthe fixed users. Thus, if a mobile entity desires to receive itsmobility related services, it must register with its designated home GK.Similarly, if a mobile entity moves to a foreign zone, it must registerwith the GK of the foreign zone, and communications with its home GKwill be done via its foreign GK (or visiting GK) to update its location.

The information related to the target GK may be useful for planningpurposes. For all GKs (target and/or home) may know a priori what may beexpected from the mobile entity in the future. However, the transportaddresses to be used in the target zone by the mobility entity may notbe known until the mobile entity registers with the target GK. If themobile entity a priori knows the transport addresses in the target zone,such addresses may be supplied.

The RRQ message is extended as follows:

The homeZone is set to TRUE to indicate that a mobile entity is seekinga registration in the home zone. The foreignZone is set to TRUE toindicate that a mobile entity is seeking a registration in a foreignzone. The homeGK is an optional message element that indicates that agatekeeper is a home gatekeeper when the mobile entity enters into theforeign zone. However, if the foreignZone field is set to TRUE, theinformation related to the home GK is supplied. The structure of thehome GK includes:

homeRASAddress—the transport address used for RAS signaling. Thisaddress is used as the home transport address for the mobile entity inits home zone.

homeCallSignalAddress—the transport address used for call signaling.This address is used as the home call signaling transport address forthe mobile entity in its home zone.

homeGKIdentifier—an optional field that is used to identify the homegatekeeper. If the homeGKIdentifier is supplied it is included in futureas messages sent:to the home gatekeeper.

careOfRASAddress—an optional field that is used to identify when amobile entity remains in its home zone, but in a subnetwork differentfrom its home subnetwork. The care-of transport address is used for RASsignaling. This address will be used as the care-of home transportaddress for the mobile entity in its home zone.

care-OfCallSignalAddress—an optional field is used to identify when amobile entity remains in its home zone, but in a different subnetworkother tan its home subnetwork. This is the care of transport addressused for call signaling. This address will be used as the care-of homecall signaling transport address for the mobile entity in its home zone.

The visitedZone is set to TRUE to indicate that the new home or foreignmobile GK needs to send the message for updating the locationinformation of the registering mobile entity to its previously visited(foreign) GK. The visitedGK is an optional message element to indicatethat the gatekeeper has been visited previously by the mobile beforemoving to its present location. However, if the visitedZone field is setto TRUE, the information related to the visitedGK field will besupplied. The structure of the visited GK includes:

visited RASAddress—the care-of transport address used by the mobileentity in the previously visited zone for RAS signaling.

visitedCallSignalAddress—the transport address used for call signaling.This address is used as the visited call signaling transport address forthe mobile entity.

visitedGKIdentifier—an optional field that is used to identify thevisited gatekeeper. If this field is supplied, it is included in futureRAS messages sent to the visited gatekeeper.

The targetZone is set to TRUE to indicate that the new home or foreignGK needs to send the message for updating the location information ofthe registering mobile entity to its targeted (foreign) GK. The targetGKis an optional message element that indicates to the gatekeeper that themobile entity intends to visit after moving from its present location.However, if the targetZone field is set to true, the information relatedto the targetGK field is supplied. The structure of the targeted GKincludes

targetRASAdddress—an optional field. This field is the care-of transportaddress used by the mobile entity in the target zone RAS signaling.

targetCallSignalAddress—an optional field. This field is the transportaddress to be used for call signaling by the mobile entity in the targetzone.

targetGIdentifier—an optional field that is used to identify the targetgatekeeper that the mobile intends to visit. If it is supplied, thetargetGKIdentifier is included in future RAS messages intended for thetarget gatekeeper.

The terminalType is an additional optional field. International MobileEquipment Identity (IMEI), International Mobile Subscriber Identity(IMSI), and Temporary Mobile Subcriber identity (TMSI) alias addressesare also included.

The homeZone and foreignZone fields are not mutually exclusive. If thehomeZone field is set to true, the foreignZone field cannot be set totrue and vice versa. If the foreignZone field is set to TRUE, the timeprovided in the timeToLive field does not exceed the time provided inthe advertisedTimeToLive field.

The visitedZone may be set independent of HomeZone, foreignZone, ortargetZone fields. The targetZone field may also be set independent ofhomeZone, foreignZone, or visitedZone fields. If the homeZone,foreignZone, visitedZone and targetZone fields are set to FALSE or noneof these extended message fields are used, it is the fixed H.323 entitythat is seeking registration with the GK. If the homeZone field is setto TRUE, the GK with which the mobile entity wishes to register is themobile entity's home GK. The RASAddress field of the RRQ message becomesthe mobile entity's hoe RAS transport address in its home zone.Similarly, the gatekeeper/Indentifier also provides the indication ofthe mobile entity's home gatekeeper in its home zone. ThecallSignalAddress field indicates that the home call signaling transportaddress of the mobile entity. The transport addresses of thealternateEndpoints become the alternate home transport addresses of themobile entity.

If the foreignZone is set to TRUE, the information related to the homeGKfield is also supplied. The mobile entity cannot provide any informationregarding its home GK unless it declares that it is in a foreign zone.The RASAddress field of the RRQ message becomes the mobile entity'care-of transport address once the mobile entity indicates that it is inthe foreign zone. Similarly, gatekeeperIdentifier also provides theindication of the mobile entity's (care-of) foreign GK in the foreignzone. The callSignalAddress field indicates the care-of call signalingtransport address of the mobile entity. The transport addresses of thealternateEndpoints become the alternate care-of transport addresses ofthe mobile entity. Moreover, additional information about thehomeRASAddresses and the homeCallSignalingAddress transport address willbe supplied by the mobile entity for indicating to its mobile GK thatthese addresses are in its home zone. The mobile entity will supply itshome gatekeeper identification in the homeGKIdentifier field.

If the visitedZone field is set to TRUE, the information related to thevisitedGK field is also supplied. The home GK or foreign GK with whichthe mobile entity is registering then proceeds to update the locationinformation about the mobile entity with the visited GK using themobility unbinding update (UbRQ/UbCF/UbRJ) or mobility binding update(BuRQ/BuCF/BuRJ) messages as appropriate. However, additionalinformation about the visitedRASAddress and thevisitedCallSignalingAddress transport address will be supplied by themobile entity to indicate to its mobile GK that these addresses had beenin its visited zone. The mobile entity supplies its visited gatekeeperinformation in the visitedGKIdentifier field.

If the targetZone is set to TRUE, the information related to thetargetGK field is also supplied. The home GK or foreign GK with whichthe mobile entity s registering then proceeds to update the locationinformation about the mobile entity with the target GK using themobility binding update messages (BuRQ/BuCF/BuRJ). The mobile entitysupplies its visited gatekeeper information in the targetGKIdentifierfield. Similarly, the transport addresses, if known, for thetargetRASAddress and the targetCallSignalingAddress fields are alsosupplied by the mobile entity.

The RCF message is extended as follows:

homeZone is set to TRUE to indicate that a mobile entity is confirmingin the home zone.

foreignZone is set to TRUE to indicate that a mobile entity isconfirming in a foreign zone.

visitedZone is set to TRUE to confirm that the GK has informed thevisited GK to update the location of the mobile entity.

targetZone is set to TRUE to confirm that the GK has informed the targetGK to update the location of the mobile entity.

As with the RRQ, the homeZone and foreignZone fields are not mutuallyexclusive. If the homeZone field is set to TRUE, the foreignZone fieldcannot be set to TRUE, and vice versa.

If the homeZone, foreignZone and the visitedZone fields are set to FALSEor none of these extended message fields are used, it is the fixed H.323entity's registration that has been confirmed with the GK.

The visitedZone field may be set independent of homeZone, foreignZone,or targetZone fields.

If the homeZone field is set to TRUE, the mobile entity has beenregistered with as its home GK and the RASAddress field sent with theRRQ message becomes the mobile entity's home transport address in itshome zone. Similarly, the gatekeeperIdentifier of the RCF message alsoprovides the indication as the mobile entity's home gatekeeper in itshome zone. The callSignalAddress field of the RCF message indicates thatthe home transport address of the array of call signaling messages ofthe mobile entity. The transport addresses of the alternateGatekeepersof the RCF message become the alternate home transport addresses of thealternate home GKs of the mobile entity.

If the foreignZone field is set to TRUE, it confirms that the mobileentity has been registered with as its foreign GK. The RASAddress fieldof the RRQ message becomes the mobile entity's care-of transport.Similarly, the gatekeeper/Indentifier also confirms the indication asthe mobile entity's care-of foreign gatekeeper GK in the foreign zone.The callSignalAddress field provides the care-of call signalingtransport address of the mobile entity. The transport addresses of thealternateGatekeepers become the alternate care-of transport addresses ofthe alternate foreign GKs of the mobile entity.

If the visitedZone field is set to TRUE, it confirms that the visited GKhas been informed by this GK (home or foreign), updating the locationinformation about the mobile entity.

If the targetZone field is set to TRUE, it confirms that the target GKhas been informed by this GK (home or foreign) updating the locationinformation about the mobile entity.

The RRJ message is extended as follows:

exceededTimeToLive is an optional field which indicates whether therequested time-to-live parameter by the mobile entity exceeds theadvertised time-to-live parameter of the mobile GK.

homeGKUnreachable is an optional field that indicates whether the homeGK is unreachable. The foreign GK with which the mobile entity is tryingto register may deny registration if it cannot reach the mobile's homeGK.

visitedGKUnreachable is an optional field that indicates whether thevisited GK is unreachable. The foreign or home GK with which the mobileentity is trying to register may deny registration if it cannot reachthe mobile's previously visited GK.

targetGKUnreachable is an optional field that indicates whether a targetGK is unreachable. The foreign or home GK with which a mobile entity istrying to register may deny registration if it cannot reach the mobile'starget GK.

Thus, selection of any or all of the message fields of theunreachability information may be decided by the particularimplementation for sending the RRJ message.

The URQ (Unregistration ReQuest) message is extended as follows:

homeZone is set to TRUE to indicate that the association between thehome GK and the mobile entity is to be broken.

foreignZone is set to TRUE to indicate that the association between theforeign GK and the mobile entity is to be broken.

As above, the homeZone and the foreignZone are not mutually exclusivefor the mobile entity. If the homeZone field is set to TRUE, theforeignZone field cannot be set to TRUE and vice versa.

If both the homeZone and the foreignZone fields are set to FALSE or noneof these extended message fields are used, it is the fixed H.323entity's unregistration that has been requested with the GK.

If the homeZone field is set to TRUE, the gatekeeperIdentifier field ofthe URQ message provides the indication as the mobile entity's alternatehome gatekeeper list in its home zone received in the RCF message fromthe gatekeeper when it registered or in a previous URJ message. This isused as a backup if the original GK did not respond or rejected therequest. The callSignalAddress field of the URQ message indicates thatthe home transport address of the array of call signaling messages ofthe mobile entity.

If the foreignZone field is set to TRUE, the gatekeeperIdentifier fieldof the URQ provides the indication as the mobile entity's (care-of)foreign gatekeeper GK list in its foreign zone received in the RCFmessage from the gatekeeper when it registered or in a previous URJmessage. The callSignalAddress field indicates the care-of transportaddress of the array of call signaling messages of the mobile entity.

The UCF (UnConFirmed) message also is extended as follows:

homeZone is set to TRUE to confirm that the association between the homeGK and the mobile entity has been broken in the mobile entity's homezone.

foreignZone is set to TRUE to confirm that the association between theforeign GK and the mobile entity has been broken in the mobile entity'sforeign zone.

As above, the homeZone and the foreignZone fields are not mutuallyexclusive for the mobile entity. If the homeZone field is set to TRUE,the foreignZone field cannot be set to TRUE and vice versa.

If both the homeZone and the foreignZone fields are set to FALSE or noneof these extended message fields are used, it is the fixed H.323entity's unregistration request that has been confirmed with the GK.

The URJ (Unregistration Request Rejection) is extended as follows:

homeZone is set to TRUE to indicate that the unregistration request hasbeen rejected in the mobile's home zone.

foreignZone is set to TRUE to indicate that the unregistration requesthas been rejected in the mobile's foreign zone.

As above, the homeZone and the foreignZone fields are not mutuallyexclusive for the mobile entity. If the homeZone field is set to TRUE,the foreignZone field cannot be set to TRUE and vice versa. If both thehomeZone field and the foreignZone field are set to FALSE or none ofthese extended message fields are used, it is the fixed H.323 entity'sunregistration request that has been rejected with the GK.

As the mobile entity moves from one point of attachment to another, itis necessary to update the new point of attachment. The messages arebinding update request (BuRQ), binding update confirm (BuCF) and bindingupdate reject (BuRJ). These messages are sent between the GKs to updateits location information as it changes its point of attachment. Uponreceiving the RRQ messages from the mobile entity, a mobile GK sends themobility binding update messages to the home and/or visited (foreign) GKas appropriate. The BURQ requests that a gatekeeper update the locationinformation related to the mobile entity. The gatekeeper responds with aBuCF confirming the update, or rejects the request with BuRJ.

The BuRQ message typically includes the following fields:

requestSeqNum is a field having a monotomically increasing number uniqueto the sender. It is returned by the receiver in any messages associatedwith the specific message sent.

nonStandardData is a field that carries information that s not defined,e.g., proprietary information.

endpointIdentifier is a field having an endpoint identifier that wasassigned to the terminal by the RCF.

replyAddress is the field showing the transport address to which to sendthe BuCF/BuRQ.

sourceInfo is the field that indicates the sender of the BuRQ. Thegatekeeper may use this information to decide how to respond to theBuRQ.

callSignalAddress is the field showing the new call signaling transportaddress for the endpoint that needs to be updated because of the changeof point of attachment. If multiple transports are supported, they mustbe updated all at once.

RASAddress is the field showing the new transport address for theendpoint that needs to be updated because of the change in the point ofattachment.

homeZone is set to TRUE to indicate that the sender of the BuRQ isrequesting the updating of the mobile entity's point of attachment inits home zone.

foreignZone is set to TRUE to indicate that the sender of the BuRQ isrequesting the update of the mobile entity's point of attachment whileit is currently visiting a foreign zone.

homeGK is an optional field that is used to indicate that the gatekeeperacts as its home gatekeeper when the mobile entity enters into thisforeign zone. However, if the foreignZone field is set to TRUE, theinformation related to the homeGK field is supplied. The structure ofthe home GK contains:

homeRASAddress—the transport address used for RAS signaling. Thisaddress is used as the home transport address for the mobile entity inits home zone.

homeCallSignalAddress—is the transport address used for call signaling.This address is used as the home call signaling transport address forthe mobile entity in its home zone.

homeGKIdentifier—is an optional field that may be used to identify thehome gatekeeper. If its is supplied, it is included for the RAS messagessent to the home gatekeeper.

foreignGK—is an optional message element that indicates the foreigngatekeeper that the mobile entity is currently visiting. However, if theforeignZone field is set to TRUE, the information related to theforeignGK field is supplied. The structure of the visited GK contains:

foreignRASAddress—the care-of transport address used by the mobileentity in the presently visited (foreign) zone for RAS signaling.

foreignCallSignalingAddress—the transport address used by the mobileentity for call signaling in its currently visited (foreign) zone. Thisaddress is used as the visited call signaling transport address for themobile entity.

foreignGKIdentifier—is the optional field used to identify the presentlyvisited (foreign) gatekeeper. If it is supplied, it is included infuture RAS messages sent to the visited gatekeeper.

visitedZone—is set to TRUE to indicate that the visiting GK has sent themessage for updating the location information of the registering mobileentity to its previously visited (foreign) GK.

visitedGK—is an optional message element to indicate the gatekeeper thathad been previously visited by the mobile entity before moving to itspresent location. However, if the visitedZone field is set to TRUE, theinformation related to the visitedGK field is supplied. The structure ofthe visited GK contains:

visitedRASAddress—the care-of transport address used by the mobileentity in the previously visited zone for RAS signaling.

visitedCallSignalAddress—the transport address used for call signaling.This address is used as the visited call signaling transport address forthe mobile entity.

visited GKIdentifier is an optional field that is used to identify thevisited gatekeeper. If it is supplied, it is included in further RASmessages sent to the visited gatekeeper.

targetZone is set to TRUE to indicate that he visiting GK has sent themessage for updating the location information of the registering mobileentity to its targeted (foreign) GK.

TargetGK is an optional message element to indicate the gatekeeper thatthe mobile entity intends to visit after moving from its presentlocation. However, if the targetZone field is set to TRUE, theinformation related to the targetGK field is supplied. The structure ofthe targeted GK contains:

targetRASAddress—an optional field that has the care-of transportaddress used by the mobile entity in the target zone RAS signaling.

targetCallSignalAddress—an optional field that has the transport addressto be used for call signaling by the mobile entity in the target zone.

targetGKIdentifier—an optional field that is used to identify the targetgatekeeper that the mobile entity intends to visit. If it is supplied,it is included in future RAS messages intended for the targetgatekeeper.

terminalType is an optional field used for International MobileEquipment Identity (IMEI), International Mobile SubscriberIdentity(IMSI) and Temporary Mobile Subscriber Identity (TMSI) aliasaddresses.

advertisedTimeToLive is a field that indicates the duration of thevalidity of the registration with the currently visiting foreign GK,typically in seconds. After this time, the gatekeeper may consider theregistration stale/no longer valid. The duration is set not to exceedthe duration of the MGA or GCF messages.

The token field contains data which may be required to allow theoperation. The data is inserted into the message if available.

The crytotoken field contains encrypted tokens.

interityCheckValue is a field used to provide improved messageintegrity/message authentication of the RAS messages. Thecryptographically based integrity check value is computed by the senderapplying a negotiated integrity algorithm and the secret key upon theentire message. Prior to the integrityCheckValue computation, this fieldis ignored and is empty. After computation, the sender puts the computedintegrity check value in the integrity check value in theintegrityCheckValue field and transmits the message.

The BuCF message typically includes the following fields:

requestSeqNum—a field having a monotomically increasing number unique tothe sender. It is returned by the receiver in any messages associatedwith the specific message sent.

nonStandardData—a field that carries information not defined, e.g.,proprietary data.

endpointIdentifier—a field having an endpoint identifier that wasassigned to the terminal by the RCF.

TimeToLive—an optional field that provides the duration, typically inseconds, of the validity of the registration with the currently visitingforeign GK. This duration is authorized by the mobile entity's home GK.After this time, the visiting foreign gatekeeper may consider theregistration stale/no longer valid. However, this duration is set not toexceed the duration of the advertisedTimeToLive field provided in theBuRQ.

homeZone—is set to TRUE to indicate that a mobile entity's locationinformation has been updated by its home GK in its home zone.

visitedZone—is set to TRUE to indicate that a mobile entity's locationinformation has been updated by a foreign GK that has been visitedpreviously by the mobile entity.

The cryptotokens field is for cryptotokens, i.e., encrypted tokens.

integrityCheckValue—is a field that provides message integrity/messageauthentication of the RAS messages. The cryptographically basedintegrity check value is computed by the sender applying a negotiatedintegrity algorithm and the secretkey upon the entire message. Prior tointegrityCheckValue computation, this field is ignored and is empty.After computation, the sender puts the computed integrity check value inthe integrityCheckValue field and transmits the message.

The BuRJ message includes the fields:

requestSeqNum—a field for a monotonically increasing number unique tothe sender.

nonStandardData—a field that carries information not defined, e.g.,proprietary data.

endpointerIdentifier—a field having the endpoint identifier that wasassigned to the terminal by the RCF.

rejectReason—a field showing the reason that the binding update relatedto the location of the mobile was denied. The structure of therejectReason is:

homeGKUnreachable—is an optional field that indicates whether themobility binding for the location update of the mobile with its home GKwas denied because the home GK could not be reached.

visitedGKUnreachable—is an optional field that indicates whether thevisited foreign GK to which the mobility binding update message is to besent cannot be reached.

targetGKUnreachable—is an optional field that indicates whether thetarget foreign GK to which the mobility binding update message s to besent cannot be reached.

notRegistered—is a field used to indicate that the mobile entity is notregistered.

invalidPermission—is a field used to indicate that exclusion is due toadministrative or other related reasons.

undefinedReason—is a field used to indicate that the reason for denialis not defined. securityDenial—is a field used to indicate that denialis due to a security reason.

The tokens field may be used to hold data that may be required to allowan operation. The data, if available, is inserted into the message.

The cryptotoken field is used for cryptotokens, i.e., encrypted tokens.

integrityCheckValue is a field that provides improved messageintegrity/message authentication of the RAS messages. Thecryptographically based integrity check value is computed by the senderapplying a negotiated integrity algorithm and the secret key upon theentire message.

As the mobile entity moves from one point of attachment to another, itis necessary to update the new point of attachment. The new mobilityunbinding messages are unbinding request (UbRQ), unbinding confirm(UbCF) and unbinding reject (UbRJ). These messages are sent between theGKs to cancel the old location information about the mobile entity.

Upon receiving the unbinding request message (UbRQ), a mobile GK cancelsthe location about the mobile entity. The UbRQ message typicallyincludes the following fields:

requestSeqNum is a field having a monotomically increasing number uniqueto the sender. It is returned by the receiver in any messages associatedwith the specific message sent.

nonStandardData is a field that carries information that s not defined,e.g., proprietary information.

endpointIdentifier is a field having an endpoint identifier that wasassigned to the terminal by the RCF.

gatekeeperIndentifier is a field having a string to identify thegatekeeper that is required to cancel the location information of themobile entity that had been in its zone.

homeGK is a field that indicates that the gatekeeper that acts as thehome gatekeeper of the mobile entity whose location information needs tobe canceled by the mobile GK. However, the structure of the home GK willtypically contain the following to identify the mobile entity uniquely:

homeRASAddress—the transport address used for RAS signaling. This is theaddress that was used as the home transport address by the mobile entitywhile it had been in this mobile entity GK's zone.

HomeGKidentifier—is an optionally included field that identifies thehome gatekeeper of the mobile entity. If it is supplied, theidentification of the home GK of the mobile entity is provided.

The tokens field may be used to hold data that may be required to allowan operation. The data, if available, is inserted into the message.

The cryptotoken field is used for cryptotokens, i.e., encrypted tokens.

integrityCheckValue—is a field that provides message integrity/messageauthentication of the RAS messages. The cryptographically based interitycheck value is computed by the sender applying a negotiated integrityalgorithm and the secret key upon the entire message. Prior tointegrityCheckValue computation, this field is ignored and is empty.After computation, the sender puts the computed integrity check value inthe integrityCheckValue field and transmits the message.

The unbinding confirm message (UbCF) confirms that the mobile GK hascancelled the location information about the mobile entity. The UbCFmessage typically includes the following fields:

requestSeqNum is a field having a monotomically increasing number uniqueto the sender. It is returned by the receiver in any messages associatedwith the specific message sent.

nonStandardData is a field that carries information that s not defined,e.g., proprietary information.

endpointIdentifier is a field having an endpoint identifier that wasassigned to the terminal by the RCF.

gatekeeperIdentifier is a field having a string to identify thegatekeeper that is required to cancel the location information of themobile entity that had been in its zone.

The tokens field may be used to hold data that may be required to allowan operation. The data, if available, is inserted into the message.

The cryptotoken field is used for cryptotokens, i.e., encrypted tokens.

integrityCheckValue—is a field that provides message integrity/messageauthentication of the RAS messages. The cryptographically basedintegrity check value is computed by the sender applying a negotiatedintegrity algorithm and the secret key upon the entire message. Prior tointegrityCheckValue computation, this field is ignored and is empty.After computation, the sender puts the computed integrity check value inthe integrityCheckValue field and transmits the message.

The Unbinding Reject (UbRJ) message typically includes the followingfields:

requestSeqNum—a field for a monotonically increasing number unique tothe sender.

nonStandardData—a field that carries information not defined, e.g.,proprietary data.

endpointerIdentifier—a field having the endpoint identifier that wasassigned to the terminal by the RCF.

rejectReason—a field showing the reason that the binding update relatedto the location of the mobile was denied. The structure of therejectReason is:

homeGKInconsistent—is an optional field that indicates whether theinformation related to the home GK of the mobile entity whose locationinformation needs to be cancelled is inconsistent.

GKUnreachable—is an optional field that indicates whether the GK towhich the mobility binding update message is to be sent cannot bereached.

notRegistered—is a field used to indicate that the mobile entity is notregistered.

invalidPermission—is a field used to indicate that exclusion is due toadministrative or other related reasons.

undefinedReason—is a field used to indicate that the reason for denialis not defined.

securityDenial—is a field used to indicate that denial is due to asecurity reason.

The tokens field may be used to hold data that may be required to allowan operation. The data, if available, is inserted into the message.

The cryptotoken field is used for cryptotokens, i.e., encrypted tokens.

integrityCheckValue is a field that provides improved messageintegrity/message authentication of the RAS messages. Thecryptographically based integrity check value is computed by the senderapplying a negotiated integrity algorithm and the secret key upon theentire message.

With regard to other H.323/H.225 signaling messages, the LRQ does notneed extensions. The LCF is generally extended as follows:

homeZone—is an optional field and can be set to TRUE or FALSE asindicated in the following table.

VisitingZone—is an optional field and can be set to TRUE or FALSE asindicated in the following table.

Visiting Home (Foreign) Zone Zone Remarks TRUE FALSE The mobile entityis providing information about its home zone and may be residing in itshome zone or in a foreign zone. If it remains in a foreign zone and doesnot wish to disclose this information, calls will be directed to itshome zone/GK. The callSignalAddress, RASAddress and alternateEndpointsfields become the address in the mobile entity's homesubnetwork/zone/GK. However, if the mobile entity is in a differentsubnetwork of the home zone other than its home subnetwork, theseaddresses will be the care-of subnetwork address of its home zone/GK. Amobile entity may also use the home subnetwork address although it is ina care-of subnetwork. In this situation, all calls of the mobile entitywill be delivered to the home subnetwork address, and it will then bedelivered to the mobile entity's care-of subnetwork address. The home GKwill take care of this. However, it may be a policy decision by themobile entity how the call will be delivered by its home GK because ahome GK will have all information available about its mobile entities itserves. FALSE TRUE The mobile entity is in its currently visited zoneand does not want to provide any information about its home zone. ThecallSignalAddress, RASaddress, and alternateEndpoints field become theaddress in the mobile entity's presently visiting subnetwork/zone/GK.TRUE TRUE Not allowed. FALSE FALSE Not allowed.

If the entity is a fixed entity, neither the homeZone or the foreignZoneis used.

The LRJ message field is typically extended as follows:

The rejectReason field includes:

invalidHomeVisitingZoneSet—if both homeZone and visitingZone are seteither to FALSE or to TRUE.

H.323 mobility management enables multimedia communications over thepacket networks for both connectionless and connection-orientednetworks. The mobility management includes the following:

Discovery

Registration

Location Updates

Call Establishment

Roaming, and

Handover (Handoff).

In H.323, call establishment and termination are performed before andafter a call. The extensions in H.323 will provide mobility serviceswith the ability to roam and implement handover. However, the callestablishment roaming and handover will be described in terms of theterminal-, user- and service-mobility.

A mobile entity may discover a mobile GK through the MGA message orsending the GRQ messages as it moves from one point of attachment toanother. Once a GK is determined, an endpoint is registered to the GKfor admission to system access through a RAS channel. However, in H.323,call establishment and termination are performed before and after acall, respectively. The extensions in H.323 in the present inventionprovide mobility services with the ability to roam and implementhandover.

A mobile entity may discover a mobile GK through the MGA message or bysending the GRQ messages as it moves from one point of attachment toanother. Once a GK is determined, an endpoint is registered to the GKfor admission to system access through a RAS channel. When a connectionhas been established for an H.323 mobile entity and the H.323 entityroams from one place to another, the point of attachment (network (e.g.,IP address) or H.323 (a zone or domain boundary)) may change. Mobile GKsmake themselves known by sending MGA advertisement messages. Theconnections may be broken unless the connection is handed off If theregistration lifetime expires, the entity is also considered to belogically disconnected. However, the discovery or detection of a newpoint of attachment can be done in one of the following ways:

Advertisement Lifetime: This method of detection is based on thelifetime field within the main body of the MGA message because theentity is not considered connected logically to the network if thelifetime for registration expires. A mobile entity records the lifetimereceived in any mobility gatekeeper advertisement (MGA) messages, untilthat lifetime expires. If the mobile entity has not maintained contactwith its mobile GK, the mobile entity must attempt to solicit a newmobile GK.

Address Prefixes of the Zone and the Network Point of Attachment: Thismethod uses the transport address prefixes (e.g., IP subnetworkaddresses or IP addresses) provided in the zoneRange field of the MGAmessage. A mobile entity can detect whether it is within a given zone ornot by examining the address prefixes of the newly received MGA message.However, a mobile entity has to know whether it is in the same ordifferent network point of attachment once it detects that it is in thesame zone. To detect whether a mobile entity is in a given network pointof attachment (e.g., IP address), or not, it has to know the networkaddress in which it has moved currently. It is a matter ofimplementation in the network layer. For example, an entity in thenetwork layer (e.g., hone/foreign agent of mobile IP) may advertise thenetwork address prefix (e.g., IP address). If an H.323 mobile entity isin a given network of a given zone, it is expected that it will receivethe advertisement message of the network by it network layer entity. Inthis way, a mobile entity can determine whether or not a newly receivedadvertised network address was received on the same subnet as the mobileentity's home or current care-of transport address. If the addressesdiffer, the mobile entity can assume that it has moved. It can beclearly seen how a mobile entity can detect whether it has moved from agiven zone to another. If it is in a given zone, it can also detectwhether it has moved from its current network point of attachment ornot.

After discovering that the mobile entity is on a foreign zone, it canobtain a new care-of transport address for this new subnetwork of a newzone from the prefix advertised by the new router and perform locationupdate procedures. In mobile H.323 (like similar procedures in mobileIP), the mobile entity's registration messages trigger a mobilitybinding at the home agent, associating the mobile entity's hometransport address with its new care-of transport address for thespecified binding lifetime.

The same registration procedure as described in the H.323 standard,which is known to those skilled in the art, is used once a GK isdiscovered, except that the extended RRQ/RCF/RRJ messages describedabove are used. In H.323, registration is the process by which anendpoint joins a Zone and informs the Gatekeeper of its TransportAddress and alias addresses. As part of their configuration process, inthe present invention, all endpoints register with the Gatekeeperidentified through the discovery process. Registration occurs before anycalls are attempted and may occur periodically as necessary (forexample, at endpoint power-up). A Gateway or MCU may register a singleTransport Address or multiple Transport Addresses. The use of multipleTransport Addresses may simplify the routing of calls to specific ports.

An endpoint sends a Registration Request (RRQ) to a Gatekeeper bysending it to the Gatekeeper's RAS Channel Transport Address. Theendpoint has the Network Address of the Gatekeeper from the Gatekeeperdiscovery process and uses the well-known RAS Channel TSAP Identifier.The Gatekeeper shall respond with either a Registration Confirmation(RCF) or a Registration Reject (RRJ). An endpoint only registers with asingle Gatekeeper.

The RRQ may be repeated periodically (i.e., at terminal power-up), sothe Gatekeeper is able to handle multiple requests from the sameendpoint. If a Gatekeeper receives an RRQ having the same alias addressand the same Transport Address as an active registration, it respondswith a RCF. If the Gatekeeper receives an RRQ having the same aliasaddress as an active registration and a different Transport Address, itmay confirm the request if it complies with the Gatekeeper's securitypolicy. Otherwise, it rejects the registration indicating a duplicateregistration. If the Gatekeeper receives an RRQ having the sameTransport Address as an active registration and a different aliasaddress, it should replace the translation table entries. The Gatekeepermay have a method to authenticate these changes.

The Gatekeeper ensures that each alias address translates uniquely to asingle Transport Address. However, an endpoint may indicate a backup,redundant or alternate Transport Address using the alternateEndpointstructure within the RAS messages. This allows an endpoint to have asecondary network interface or a secondary H.323 endpoint as a backup.Ambiguous registrations are rejected by the Gatekeeper. The Gatekeepermay reject the registration for other reasons, such as changes indiscovery or security issues.

If the endpoint does not include an alias address in the RRQ message,the Gatekeeper may assign one. The Gatekeeper shall return the assignedalias address to the terminal in the RCF message.

Each mobile entity has a finite registration life and requires aregistration during roaming. A mobile entity's location is updated usingthe registration (RRQ/RCF/RRJ) and mobility binding(BuRQ/BuCF/BuRJ)messages. The updating of the mobile's location as it moves from onesubnet to another or from one zone to another, is known as the mobilitymanagement.

In one embodiment, a computer-readable medium 702 havingcomputer-executable steps may be utilized for implementing, by a MobileTerminal Node/Entity, an H.323-based mobility protocol for real-timemobile multimedia communications and conferencing over packet-basednetworks wherein a plurality of H.323 mobility gatekeepers providenotification of H.323 mobility services availability by periodicallybroadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisementwith a multicast address. As shown in FIG. 7, the computer-executablesteps typically include: (1) where the Mobile Terminal/Node/Entitybecomes mobile and initiates an H.323 communication that includes atleast one of: audio, video and data, by the Mobile Terminal/Node/Entity,with respect to notification 704, one of: providing, by at least one ofa plurality of available H.323 Home/Foreign Mobility Gatekeepers,notification of H.323 mobility services availability by periodicallybroadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisementwith a multicast address; and where the Mobile Terminal/Node/Entitylacks notification of H.323 mobility services availability, sending, bythe Mobile Terminal/Node/Entity, a message to the Home Gatekeeper/HomeLocation Database, which notifies H.323 Home/Foreign MobilityGatekeepers in a preselected area local to the MobileTerminal/Node/Entity that the Mobile Terminal/Node/Entity needs H.323mobility services and notifying, by.the H.323 Home/Foreign MobilityGatekeepers, the Mobile Terminal/Node/Entity of available H.323Home/Foreign Mobility Gatekeepers; (2) registering 706, by the MobileTerminal/Node/Entity, with a H.323 Home/Foreign Mobility Gatekeeper ofthe available H.323 Home/Foreign Mobility Gatekeepers that support H.323mobility services in a Location Area/Cell/Zone of the MobileTerminal/Node/Entity; and (3) providing 708, for the MobileTerminal/Node/Entity by the H.323 Home/Foreign Mobility Gatekeeper withwhich the Mobile Terminal/Node/Entity is registered, support for theH.323 communication that includes at least one of: audio, video anddata.

Registering with the H.323 Home/Foreign Mobility Gatekeeper may includesending registration information for the Mobile Terminal/Node/Entityusing a Base Station to Base Station Controller to Mobile SwitchingCenter to H.323 Home/Foreign Gatekeeper system. Alternatively,registering with the at least one H.323 Home/Foreign Mobility Gatekeepermay include sending registration information for the MobileTerminal/Node/Entity using a wireless/wire-line Local Area Network toRouter/Switch to H.323 Home/Foreign Gatekeeper system.

In one embodiment, registering may include the steps of:

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, aMobility Gatekeeper Advertisement (MGA) message periodically;broadcasting/multicasting/sending a registration request message (RRQ)to the Home Gatekeeper by the Mobile Terminal/Node/Entity; and sending,by the Home Gatekeeper, a registration confirmation/registrationrejection (RCF/RRJ) to the Mobile Terminal/Node/Entity.

In another embodiment, registering may include the steps of: upondetermining, by the Mobile Terminal/Node/Entity, that a network point ofattachment has changed/a foreign zone has been entered,broadcasting/multicasting/unicasting/sending, by the MobileTerminal/Node/Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a binding update message (BuRQ) to the Home Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, abinding update confirmation/rejection (BuCF/BuRJ) to theForeign/Visiting Gatekeeper; andbroadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, the binding update confirmation/rejection to the MobileTerminal/Node/Entity.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, amobility unbinding message (UbRQ) to the Visited Gatekeeper; and

broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the HomeGatekeeper.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:

broadcasting/multicasting/unicasting/sending, by the MobileTerminal/Node/Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a mobility unbinding update message (UbRQ) to the VisitedGatekeeper;

broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to theForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a provisional registration confirmation to the MobileTerminal/Node/Terminal and

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a binding update message (BuRQ) to the Home Gatekeeper; andbroadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, abinding update confirmation/rejection (BuCF/BuRJ) to theForeign/Visiting Gatekeeper.

Where the Mobile Terminal/Node/Entity has already visited anotherforeign zone regulated by a Visited Gatekeeper, registering may include:

broadcasting/multicasting/unicasting/sending, by the MobileTerminal/Node/Entity, a registration request message (RRQ) to aForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to theForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a provisional registration confirmation to the MobileTerminal/Node/Terminal and

broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a binding update message (BuRQ) to the Home Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, abinding update confirmation/rejection (BuCF/BuRJ) to theForeign/Visiting Gatekeeper;

broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, amobility unbinding update message (UbRQ) to the Visited Gatekeeper; and

broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the HomeGatekeeper.

In one embodiment, at least one Home/Foreign Gatekeeper utilizes acombined Home/Visitor Location Database. In another embodiment, aplurality of Home/Foreign Gatekeepers each utilize an individual VisitorLocation Database and share a Home Location Database.

Where the Mobile Terminal/Node/Entity is originally located in a FirstAdministrative Domain and is moving in a Second Administrative Domain,registering may sending/sending a registration request message (RRQ), bythe Mobile Terminal/Node/Entity to the Foreign/Visiting Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Foreign/VisitingGatekeeper, a mobility unbinding (UbRQ) message to a Visited Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper,an unbinding confirmation/rejection (UbCF/UbRJ) to the Visiting/ForeignGatekeeper; broadcasting/multicasting/unicasting/sending, by theVisiting Gatekeeper, a provisional registration message to the MobileTerminal/Node/Entity; broadcasting/multicasting/unicasting/sending, bythe Foreign/Visiting Gatekeeper, a mobility binding message (BuRQ) to aBorder Element of the Second Administrative Domain, which forwards themessage to a Border Element of the First Administrative Domain whichthen forwards the message to the Home Gatekeeper;broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, amobility binding confirmation/rejection (BuCF/BuRJ) message to theBorder Element of the First Administrative Domain, which forwards themessage to the Border Element of the Second Administrative Domain, whichforwards the message to the Visiting Gatekeeper.

As shown in FIG. 8, in one embodiment when a mobile H.323 entityperforms intra-zone roaming, the location may be updated. Where themobile H.323 entity 802 has moved from subnetwork 1 804 to subnetwork 2806 within its Home Zone 810, it may detect its new network point ofattachment in two ways, as described more fully above. The mobile H.323entity acquires the new temporary care-of network address dynamically(e.g., DHCP in the case of an IP network). Although the mobile H.323entity is still under the control of the same GK 808, the mobile H.323entity's new network attachment needs to be updated with its home GK808. The following steps may be taken to update the location of themobile H.323 entity:

1: The MGA message advertised by the mobile (home) GK is received by themobile entity. The mobile entity detects whether its network point ofattachment has been changed (as described above).

2: The mobile entity then initiates the RRQ message with its presentcare-of network address for re-registration. A mobile entity may alsodetect the change in its subnetwork point of attachment without the helpof the MGA message. If it has changed, it can also send the RRQ messageto its home GK for re-registration. In the extreme situation, a mobilemay also send the GRQ message to find its GK ad the usual GCF/GRJmessages will follow (not shown).

3: The usual RCF/RCF messages will follow.

In this way, the home GK may update the location information about themobile entity. The mobility binding messages (BuRQ/BuCF/BuRJ) aretypically not involved for this situation. In some instances, the mobileentity might have been communicating with an entity located within aforeign zone or the mobile has just returned from the foreign zone toits home zone. In those cases, the home GK needs to update those foreignGKs about the location of the mobile entity using the BuRQ/BuCF/BuRJmessages.

As shown in FIG. 9, a mobile H.323 entity 902 may roam from zone to zone(inter-zone), and the system then updates the subscribed mobile H.323entity's location. Upon crossing a zone boundary, the H.323 mobileentity may receive the MGA message broadcast/multicast/unicast by theforeign (visiting) GK 904. If the mobile H.323 entity receives the MGAmessage, it will send the RRQ message to the visiting GK 904.Alternatively, the mobile H.323 entity ma also send the GRQ messageseeking a registration for the foreign GK if no MGA message is received,and the usual GCF/GRJ messages will be exchanged before sending theregistration message (event 1). These steps are not shown in FIG. 9 forsimplicity. The following events describe how the location update isdone once the registration with the visiting GK is sought by the mobileH.323 entity:

Event 1: The RRQ message is sent by the mobile H.323 entity 902 to itsvisiting GK 904.

Event 2: The visiting GK 904 has no information about the entry of themobile H.323 entity 902 because this new entity has moved in its servingzone recently. However, the visiting GK 904 needs to update the mobileH.323 entity's location to the home GK of the mobile H.323 entity 902.Receiving the RRQ message, a mobile/visiting GK 904 then knows where themobility binding needs to be done. In this example, the visiting GK 904sends the BuRQ message to the mobile H.323 entity's home GK 906. Thismessage includes the identity of the mobile H.323 entity 902 as well asthe identity of the visiting GK 904 that sent the message.

Event 3: Upon receiving the BuRQ message, the home GK 906 stores themobile entity's new location at the visiting GK 904 and examines themobile entity's information (e.g., user profiles, calling originationand termination services, authentication parameters, accountinginformation; subscriber services, etc.). The home GK 906 sends theconfirmation (BuCF) or rejection (BuRJ) message with respect to themobile H.323 entity's new location to the visiting GK 904.

Event 4: Accordingly, upon receiving this information (BuCF or BuRJ),the visiting GK 904 sends registration confirmation (RCF) or rejection(RRJ) message to the mobile H.323 entity 902.

Event 5: The mobile H.323 entity 902 may have already visited anotherforeign zone (visited zone) before moving to the visiting zone. The BuRQmessage also indicates whether or not the updating message has been sentto the visited GK 908 by the visiting GK 904, and the home GK 906 sendsthe mobility unbinding message UbRQ for updating the location to thevisited GK 908 related to the H.323 mobile entity's information in itsdatabase. In some situations, the mobility binding message (BuRQ) mayalso be sent for updating without deleting the previous information. Itis a matter of implementation and will not be described here.

Event 6: In turn, the visited GK 908 sends the mobility unbindingconfirmation (UbCF) or rejection (UbRJ) message to the home GK 906. Themobility binding confirmation (BuCF) or rejection (BuRJ) message is sentif the BURQ message is sent in event 5.

The mobile subscriber entity (mobile H.323 entity) is known only to oneforeign/visited GK at a time. In this example, when the mobilesubscriber entity has roamed to another zone, the home GK 906 has had tobe updated.

The home GK 906 is the master of the mobile H.323 entity's informationbase (may act as the master database of the motile entities) andtherefore, coordinates changes to the visiting-and visited-GKs as themobile subscriber entity roams through the zones. If needed, theinformation related to the targeted GK (not shown in this example) mayalso be coordinated by the home GK.

As described above, as the mobile entities move from one point ofattachment to the next between zones, location updates using themobility binding messages is smooth. For example, a home GK may be toofar away from the mobile H.323 entity's visiting- and visited-zone torespond in time. If the responses for the updates require a GK to waitfor a hundred milliseconds, for example, the system's response time willincrease significantly. In such cases, a smooth location update may beimplemented by cooperation between the visiting- and visited-GK withoutthe involvement of the home GK where the mobile H.323 entity authorizesthe visiting GK to perform smooth location update handoffs before thenew registration is completed with its home GK.

As shown in FIG. 10, smooth location updates are obtained duringregistration. A domain may consist of multiple zones. AN H.323 mobileentity 1002 may move between zones of a given administrative domain.FIG. 10 depicts smooth location updates using the mobility bindingmessages in a single administrative domain 1004. The MGA (or(GRQ/GCF/GRJ) messages that may be required before sending the RRQmessages is now shown here for simplicity. The sequence of events shownin FIG. 10 is as follows:

Event 1: The mobile H.323 entity 1002 sends the RRQ message to thevisiting GK 1006 authorizing it to make smooth location updates throughcommunicating with the previously visited GK 1008 before performing thelocation update with its home GK 1010.

Event 2: The visiting GK 1006 sends the mobility unbinding (UbRQ)message to the designated visited GK 1008 of the mobile H.323 entity1002. This message includes the identity of the mobile H.323 entity 1002as well as the identity of the visiting GK 1006 that sent the message.

Event 3: The previously visited GK 1008 of the mobile H.323 entity 1002confirms or rejects the mobility unbinding update using the UbCF or UbRJmessage.

Event 4: Upon receiving this information, the visiting GK 1006 confirmsthe mobility binding to the mobile H.323 entity 1002 so that a smoothlocation update takes place before the location update is completed withthe home GK 1010. However, it is a provisional registration of thevisiting mobile H.323 entity 1002 because the mobile H.323 entity's homeGK 1010 also needs to confirm the binding.

Event 5: The visiting GK 1006 also sends the mobility binding update(BURQ) message to the mobile H.323 entity's home GK 1010. This messageincludes the identity of the mobile entity as well as the identity ofthe visiting GK 1006 that sent the message. Events 2 and 5 may takeplace simultaneously.

Event 6: Upon receiving the mobility updating message (BuRQ) message, asbefore, the home GK 1010 stores the mobile H.323 entity's new locationat the visiting GK 1006 and examines the mobile entity's information(e.g., user profiles, calling origination and termination services,authentication parameters, accounting information, subscriber services,etc.). The home GK 1010 sends the mobility binding information (BuCF) orrejection (BuRJ) message to the visiting GK 1006. In the case ofconflicting messages from the home GK 1010 and the visited GK 1008, thehome GK 1010 prevails. If the home GK 1010 determines that the visitingGK 1006 has sent the location update information to the visited GK 1008,it will update the information related to the visited GK 1008 and theevents 6 and 7 will not take place.

Event 7: If event 2 does not take place, the home GK 1010 will send themobility unbinding (UbRQ) message to the visited GK 1008.

Event 8: Accordingly, the visited GK 1008 will send the mobilityunbinding confirmation (UbCF) or rejection (UbRJ) message. This event(8) will not take place if event 7 does not take place.

A mobile H.323 entity may be moving in a separate administrative domainother than its own. FIG. 11 is a block diagram showing a high levelimplementation of events especially related to location updates when amobile H.323 entity 1102 moves from one administrative domain(Administrative Domain 1) 1104 to a next administrative domain(Administrative Domain 2) 1106 and smooth location updates areimplemented during registration. The mobile H.323 entity 102 has movedfrom its visited zone 1108 to the visiting zone 1110 in AdministrativeDomain 2 1106 while its home zone remains in Administrative Domain 11104. For FIG. 11, the following events take place (event numbers areshown in FIG. 7):

Event 1: The mobile H.323 entity sends the RRQ message to the visitingGK 1110 authorizing it to make a smooth location update with thepreviously visited GK 1108 before performing the location update withits home GK 1112.

Event 2: The visiting GK 1116 sends the mobility unbinding (UbRQ)message to the designated visited GK 1114 of the mobileH.323 entity1102. This message includes the identity of the mobile H.323 entity 1102as well as the identity of the visiting GK 1116 that sent the message.

Event 3: The previously visited GK 1114 of the mobile H.323 entity 1002confirms or rejects the mobility unbinding update using the UbCF or UbRJmessage.

Event 4: Upon receiving this information, the visiting GK 1116 confirmsthe mobility binding to the mobile H.323 entity 1102 so that a smoothlocation update takes place before the location update is completed withthe home GK 1112. However, it is a provisional registration of thevisiting mobile H.323 entity 1102 because the mobile H.323 entity's homeGK 1112 also needs to confirm the binding.

Event 5: The visiting GK 1116 sends a mobility binding message (BuRQ) tothe Border Element (BE/GK) 1118 of the Administrative Domain 2 1106,which forwards the message to the Border Element (GK/BE) 1120 of theAdministrative Domain 1 1104, which then forwards the message to theHome GK 1112.

Event 6: The Home GK 1112 sends the mobility binding information (BuCF)or rejection (BuRJ) message to the Border Element (GK/BE) 1120 ofAdministrative Domain 1 1104, which forwards the message to the BorderElement (BE/GK) of Administrative Domain 2 1106, which forwards themessage to the visiting GK 1116.

Each mobile H.323 entity needs to register with its home GK. The mobileH.323 entity designates its home GK to become the central controllingpoint to manage its mobility. Even if a mobile H.323 entity moves to aforeign zone, it needs to register with a foreign GK. As a result, a GKneeds to manage the location information for both home and foreignvisitors. Typically, a GK maintains databases (home/visitor location)for keeping the location information of both home and visitor locationinformation. FIG. 12 is a block diagram showing one embodiment of adistributed architecture for home/foreign zones 1202, 1204, 1206, 1208;home/foreign GKs 1210, 1212, 1214; and home/visitor location databases1216, 1218, 1220.

In H.323, the services between the GK and the location database areknown as the backend services, and the protocol between these functionalentities are known as the backend services protocol. Both the backendservices and the protocol have not yet been standardized in H.323.

FIG. 13 is a block diagram showing one embodiment of an optimizeddistributed architecture for home/foreign zones 1302, 1304, 1306, 1308;home/foreign GKs 1310, 1312, 1314; visitor location databases 1316,1318, 1320; and a home location database 1322 in accordance with thepresent invention. By separating the visitor location databases 1316,1318, 1320 from the home location database and providing the homelocation database as a single, centralized home location database 1322accessible by the home/foreign GKs 1310, 1312, 1314, management issimplified. Because the home location of a mobile H.323 entity remainsthe same, and this information may be kept in a central home locationdatabase. However, the scalability of such an optimization scheme may beexamined, especially in the context of a large-scale IP network or thepublic Internet. There may also be hierarchical databases for managingthe location information. The choice of a distributed vs. a centralizedlocation management database is a matter of choice of implementation.

Location management involves the updating of location databases whencurrent location information is available. During the callestablishment, these databases are queried to determine the currentlocation of the mobile entity. These can be costly processes especiallywhen the mobile entity is located far away from its assigned home GK.So, the location management may need to be further optimized.Figure—shows one such example where the location of the home locationinformation has been centralized. In this centralized home locationdatabase architecture, the management may be little simpler because thehome location of a mobile entity remains the same and this informationmay be kept in a central database. However, the scalability of thissolution can be examined especially in the context of the large-scale IPnetwork or the public Internet. There can also be hierarchical databasesfor managing the location information. The choice of a distributive vs.a centralized location management database is a matter ofimplementation.

The present invention provides the ability for a terminal to change itslocation. The change of location may be the network point of attachmentor the H.323 point of attachment. Even if the terminal changes itslocation, an H.323 entity will still be able to communicate. Thefollowing description provides an example of how a terminal will makediscrete changes of physical location (i.e., to change location while nomedia streams are active). In addition, a terminal will be able tochange its location while media streams are active where handoffs needto be provided.

In both wireless and wire-line networking environment, terminal mobilitymay be provided with discrete changes of physical locations where nomedia streams are active. However, a terminal may change its locationwhile media streams are active only for the wireless network.

In H.323, it is considered that there is a single GK in a zone and thesaid GK manages the information of the fixed (non-mobile)- andmobile-entity. So, the same GK can also perform the function of thefixed- and mobile (home/foreign/visiting/visited/target)-GK. An H.323mobile terminal may roam within a zone, between the zones (inter-zone),or between domains (inter-domain). A call may have to be establishedbetween the fixed and mobile H.323 terminals. The terminals may locatedwithin the same zone, different zones and/or different domains. However,handover (or handoff) management enables the H.323 system to maintaincommunications as the mobile terminal continues to move and change itspoint of attachment. The following steps are involved for the handover:

The process for handoff first involves initiation, where either theuser/terminal, a GK, or changing system conditions (e.g., point ofattachment) identify the need for handoff.

The next stage is the new connection generation, where the system mustfind new resources for handoff a connection and perform the connectionto the new location (this may also involve additional routing operationsat the lower transport layer).

The final stage is the media-flow control, where the delivery of themedia from the old connection path to the new connection path (the term“connection” is used as an abstraction in the higher H.323 layeralthough the lower transport layer (e.g., IP, ATM) may or may not havethe concept of connection) is maintained accordance to the agreed-uponservice conditions. It is important to note that the changeover betweenthe old and new connection during the handoff requires these twoconnections to coexist for a brief period of time until the transitionoccurs successfully. This transition between the old and new connectionduring the handoff can be handled dynamically using the H.323's joiningand leaving an ad hoc multipoint conference. In this way, creation ofany new signaling messages to support handoff is avoided.

In H.323, an ad hoc conference may be created with the help of amultipoint controller (MC) or a multipoint controller unit (MCU) so thata new endpoint can join the conference: (request-to)-join (by requestingon its own) and invite-(to-join) (being invited by any participant).That is, the same mobile terminal will have two logical entities, onefor the old point of attachment and the other for the new point ofattachment for a brief period of time. As soon as the mobile entityfinds that the transition has been completed successfully, the old pointof attachment is terminated issuing the leave conference indication withendSessionCommand, while the communications with the new point ofattachment will continue. Thus, the handovers can be provideddynamically using the mobile H.323 protocol of the present invention. AnH.323 entity that needs to use this capability needs to have the MCcapability. This feature may be realized within a GK, MCU, GW, orterminal.

The call made between H.323 entities may be: fixed-to-mobile,mobile-to-fixed, or mobile-to-mobile. However, the call may beintra-zone, inter-zone, or inter-domain. FIG. 14 shows all fixed 1402and mobile 1404 H.323 entities residing within a single zone. However, azone may have many subnetworks. A call may take place between differentH.323 entities using the new and/or extended H.323 signaling messages.The subsequent messages will describe various call scenarios.

FIGS. 15(a)-(b) show the call flows where a fixed entity 1502, 1506 hascalled a mobile entity 1504, 1508. These entities are in the same zone,but they may be in the same subnetwork or in separate subnetworks (seeFIG. 14). The flows are self-explanatory. There may be some differencesin the pre-call setup scenarios depending whether or not the mobile isregistered with its home GK. If the mobile is not registered with itshome GK either due to expiration of the registered lifetime or due tochange in the subnetwork point of attachment, the home GK needs to sendthe LRQ message using the paging in all subnetworks in its zone tolocate the mobile because the GK will not have any idea where the mobileis residing. All other flows remain the same as in the case of thetraditional fixed or non-mobile H.323 situations.

FIGS. 16(a)-(b) show the call flows where a mobile entity 1602, 1606 hascalled a fixed entity 1604, 1608. These entities are in the same zone,but they may be in the same subnetwork or in separate subnetworks (seeFIG. 14). This situation is somewhat straightforward because the mobileneeds to be registered with its home GK before a call is made. FIGS.16(a)-(b) depict a situation that the mobile registers with the GK afterreceiving the MGA message. If the mobile does not receive the MGAmessage, it may also send the GRQ message to discover the mobile GKbefore registration. However, this situation is not shown forsimplicity. All other signaling flows remain the same as in the case ofthe traditional fixed or non-mobile H.323 situation.

FIGS. 17(a)-(b) show the call flows where a mobile entity 1702, 1706 hascalled another mobile entity 1704, 1708. These entities are in the samezone, but they may also be in the same subnetwork or in separatesubnetworks (see FIG. 14). The calling mobile entity needs to registerwith its home GK before the call is established. The called mobileentity may or may not be registered with the mobile (home) GK. Dependingon these situations, the pre-call setup scenarios will vary. FIGS.17(a)-(b) show the probable pre-call setup cases. The remaining callestablishment flows remain the same as in the case of the traditionalH.323 cases.

H.323 entities will remain in multiple zones while they will becommunicating among themselves. FIG. 18 shows only two zones with fixed1802 and mobile 1804 entities for simplicity. The two entities locatedin two different zones may communicate directly. However, the call canalso be the GK-routed. In this example, it is assumed that the call willbe routed via the calling party's GK. The fixed entity 1802 is locatedin zone 1 1806 while the mobile entity 1804 is situated in zone 2 1808.Zone 2 is also termed as the home GK of the mobile entity. It isconsidered that the mobile entity is in its home zone, and then theattempt is made to establish the call.

FIGS. 19(a)-(b) depict call signaling between the fixed 1902, 1906 andthe mobile 1904, 1908 entity located in two different zones: (a) Directand (b) GK-routed. There may be two scenarios for the pre-call setup.The mobile may or may not be registered with its home GK. Once themobile is registered, the call establishment will proceed, as discussedearlier, in accordance to the traditional H.323 call flows (case-1). Incase-2, where the mobile is not registered, GK 1 of the fixed entitywill send the LRQ message to the mobile's home GK 2. GK 2 has no ideawhere the mobile entity is. So, GK 2 will page the LRQ message in itsown zone. The mobile will then proceed to register with the home GK. Themobile will send the location confirmation (LCF) message once theregistration is completed. The LCF message will then be relayed back toGK 1 by GK 2. The rest of the call flows is the same as that of thetraditional H.323 call establishment.

Mobile to fixed transmission may be explained in a similar way that hasbeen described in the case of the fixed-to-mobile situation.

FIG. 20 shows two mobile entities 2002, 2004 that are located in twoseparate zones. It is assumed that these entities are located in theirrespective home zones.

FIGS. 21(a)-(b) provide the call flow scenarios for the mobile-to-mobilecommunications while these entities are located in two separate zones:(a) Direct and (b) GK-routed. The calling mobile entity 2102, 2106 shallregister with its home GK before the call is made to the called mobileentity 2104, 2108. The mobile GKs will advertise the MGA message intheir respective zones. The registration can be made after receiving theMGA message as shown in FIG. 21. The mobile entity can also send the GRQmessage to discover the mobile GK and the GCF/GRJ messages will alsoflow accordingly. This alternatively scenario has not been shown forsimplicity. As before, there can be two scenarios for the pre-callsetup. Once the mobile is registered, the call establishment willproceed, as discussed earlier, in accordance to the traditional H.323call flows (case-1). In case-2, where the mobile is not registered, GK 1of the fixed entity will send the LRQ message to the mobile's home GK 2.GK 2 has not idea where the mobile entity is. So, GK 2 will page the LRQmessage in its own zone. The mobile will then proceed to register withthe home GK. The mobile will send the location confirmation (LCF)message once the registration is completed. The LCF message will then berelayed back to GK 1 by GK 2. The rest of the call flows is the same asthat of the traditional H.323 call establishment.

In the preceding examples, it was shown how the calls are establishedwith the mobiles in many situations (e.g., fixed-to-mobile,mobile-to-fixed, or mobile-to-mobile). The conversations will go onafter the call establishment while the mobile will move from one placeto another (in wireless environment). The movement may cause the changein point of attachment (e.g., IF subnetwork address in a given zone orin a different zone). The detection in change of point of attachmentwill initiate a new connection to the new point of attachment (whilekeeping the old connection until the transition occurs to the newconnection properly). As soon as the resources are allocated to the newconnection, the old connection and the resources to the old connectionis terminated.

As explained earlier, the transition from the old connection to the newconnection during the handoff can be made via an H.323 communicatingentity that can create ad hoc multipoint conferencing either from thepoint-to-point or from the multipoint call using the multipointcontroller (MC). As a part of multipoint conference setup, an endpoint(H.323 entity) will become connected to an MC on its H.245 controlchannel.

In the intra-zone call scenario, a mobile entity is communicating(audio, video, and/or data) with another H.323 entity (fixed or mobile)in the same zone. The call may be established either directly or via theGK. It is assumed that one of the communicating H.323 entities will havean MC that can create the ad hoc multipoint conferencing to providetransition from the old connection to the new one during handover. FIGS.22(a)-(b) depict a situation for the intra-zone handover where a callcan be either directly routed or GK routed.

FIG. 22(a) shows the directly routed call between a fixed 2202 and amobile 2204 entity while the fixed entity has the MC capability. In FIG.22(b), the call is routed via the GK 2206 and the GK has the MCcapability. The subsequent sections describe the detail call signalingduring handoffs. In this scenario (FIG. 22(a)), it is assumed that theconversations with audio, video, and/or data between the fixed and themobile entity are going on while both entities are in the subnetwork 1of (home) zone 1 and the mobile entity is moving from one place toanother. Let us assume that the mobile terminal (MT) designates thisconnection as MT1 with the fixed terminal (FT). Now suppose that themobile entity's network point of attachment (e.g., IP subnetworkaddress) changes as it moves from subnetwork 1 to subnetwork 2. Themobile can detect the change in the network point of attachment in oneof the two ways as discussed earlier.

FIG. 23 shows the call flows that include the intra-zone handover from afixed entity 2302 with MC capability for a directly routed call to amobile entity 2304 as the mobile moves from subnetwork 1 to subnetwork2. The following steps describe the call signaling on how the handoff isprovided as the new connection is established while the old connectionis terminated:

Step 1: The MGA message is advertised by the (home) GK in its (home)zone. The mobile terminal receives the MGA message and confirms that itstill in its home zone. (Then it also examines that the address ofsubnetwork 2 (e.g., IP address) in which it has moved presently. Thesubnetwork address is being advertised in the network layer (e.g.,mobile IP's home/foreign agent). This is a matter of implementation inthe network layer and, H.323 does not deal with the implementation inthe network layer.) The mobile terminal confirms that it has moved tothe new subnetwork and needs to re-register with its home GK. (Inanother scenario, the mobile terminal can also initiate the GRQ messageto find the GK for registration should it not receive the MGA message.This possibility is not shown for simplicity.)

Step 2: The mobile terminal sends the RRQ message for registration withthe home GK This message will contain the mobile terminal's home andcare-of network addresses (e.g., IP addresses) in addition to otherinformation.

Step 3: The (home) GK sends the registration confirmation (RCF) orrejection (RRJ) message.

Step 4: The mobile terminal sends the admission request (ARQ) message toits home GK as a precursor for establishment of a new connection in itsnew point of attachment after receiving the registration confirmation(RCF) message.

Step 5: The (home) GK sends the admission confirmation (ACF) orrejection (RRJ) message to the mobile terminal based on the fact whetherthe requirements for the admission can be met or not. In ACF, the GKreturns a call signaling channel transport address of the fixed terminal(FT).

Step 6: The mobile terminal sends the Setup message to the fixedterminal for joining the same on-going conference (CID=K) afterreceiving the admission confirmation (ACF) message using that transportaddress of the fixed terminal. It is seeking a new connection (MT2) forthe same conference (CID=K) that was used for the previously establishedconference between the mobile terminal (MT1) and the fixed terminal(FT).

Step 7: The fixed terminal sends the Call Proceeding/Alert messageindicating that the called fixed terminal has been alerted with the newconnection (MT2).

Step 8: The fixed terminal (FT) responds with the Connect message whichcontains an H.245 control channel transport address for use in H.245signaling for the new connection (MT2). The fixed terminal withmultipoint controller (MC) will associate this new call of the newconnection (MT2) for the same conference (CID=K).

Step 9: H.245 message exchanges take place between the fixed and themobile terminal and the detail has not been shown for simplicity. Mediachannels (audio, video, and/or data) for communications between thefixed terminal (FT) terminal (having the MC capability) and the mobileterminal's new connection (MT2) are opened.

Step 10: Conversations (audio, video, and/or data) between the FT (fixedterminal) and the MT2 (mobile terminal's new connection) take place.

Step 11: The mobile terminal issues the H.245 endSessionCommand messagein the H.245 control channel, indicating to the fixed terminal that itwishes to disconnect the old call (for the old connection MTI) and thendiscontinues the H.245 message transmission.

Step 12: The fixed terminal responds with.the H.245 endSessionCommandmessage in the H.245 control channel for termination of the old call(for the old connection MT1).

Step 13: Then the fixed terminal sends the releaseComplete messageindicating the old call (for the old connection MT1) has beenterminated. (It may be noted that the conference (CID=K) between thefixed terminal (FT) and the mobile terminal's new connection (MT2) isstill going on although the old connection MT1 has been released.)

Step 14: The mobile terminal sends the H.225.0 disengage request (DRQ)message to its home GK to release the resources used for the oldconnection (MT1).

Step 15: The (home) GK responds with the H.225.0 disengage confirm (DCF)message after releasing the resources used for the old connection (MT1).

In this way, a new connection is established with the fixed terminal andthe mobile terminal (MT2). The handover is provided form the old (MT1)to the new connection (MT2) via the MC located within the fixedterminal. It is expected that there might be a situation where both theold and the new connection might co-exist for a very brief period oftime before the successful handoff is made.

FIG. 22(b) shows the intra-zone communications where the call is routedvia the GK that has the MC capability. This case is similar to that ofthe scenario for the directly routed call with the fixed terminal havingthe MC capability. The exception is that the GK with its MC that iscontrolling the call is priori involved in the beginning of theconference. The point-to-point call between the fixed and mobile entityis being made via the GK (with its MC) and H.245 control channels arealso being established via the GK before the handover is made.

FIG. 24 shows the call signaling for the GK-routed handover from a fixedH.323 terminal 2402 to a mobile H.323 terminal where the GK has MCcapability. It is assumed that a point-to-point call has beenestablished between the fixed and the mobile entity via the GK (withMC). This also means that H.245 control channels have also beenestablished via the GK. The steps 1 through 15 are similar to those thathave been shown as in the case of the directly routed call. Theexception is that the GK (with MC) will be involved to provide thehandover from the old connection (MT1) to the new connection (MT2)instead of the fixed terminal (with MC).

FIGS. 25(a)-(b) show inter-zone handoffs that are needed for a (a)Directly Routed Call and a (b) GK-Routed Call because the mobile entitymoves out of the zone boundary. It is assumed that the call has alreadybeen established between the fixed and mobile entity before the handoff.The inter-zone handoff is needed as the mobile terminal moves from onezone to another. Initially, a mobile entity 2502 is communicating(audio, video, and/or data) with another H.323 entity (fixed or mobile)2504 in the same zone. The call is established either directly or viathe GK. It is assumed that one of the communicating H.323 entities willhave an MC that can create the ad hoc multipoint conferencing to providetransition from the old connection to the new one during handover. TheMC will also be connected using H.245 channels.

The subsequent descriptions provide for the inter-zone handoffs for thedirectly- and GK-routed call. Again, it may be noted that an MC isneeded to provide the handoff.

In FIG. 25(a), it is assumed that the conversations (with audio, video,and/or data) are going on between the fixed and the mobile entity whileboth entities are in zone 1 and, the mobile entity is moving from oneplace to another. However, it is considered that the fixed entity hasthe MC capability to create the ad hoc multipoint conferencing. Asbefore, let us assume that the mobile terminal (MT) designates thisconnection as MT1 with the fixed terminal (FT). Now consider that themobile entity's zone point of attachment (e.g., a group of IP subnetworkaddresses in a given zone) changes as it moves from zone 1 to zone 2.The mobile can detect the change in the zone point of attachmentdirectly through examining the MGA message (e.g., zoneRange) receivedfrom the mobile GK in a given zone.

FIG. 26 shows the call flows that includes the handover as the mobilemoves from (its home)zone 1 to visiting/foreign zone 2, i.e., callsignaling for inter-zone handovers: fixed entity 2602 with MC capabilityfor the directly routed Call to the mobile terminal 2604. The followingsteps describe the call signaling for the inter-zone handoff that isprovided as the new connection established while the old connection isterminated:

Step 1a: The MGA message is advertised by the (visiting/foreign) GK by(mobile visiting/foreign GK 2. The mobile terminal receives the MGAmessage and confirms that it has moved to a foreign zone. The mobileterminal confirms that it has moved to a new foreign zone and needs toregister with visiting/foreign GK 2.

Step 1b: In another scenario, the mobile terminal can also initiate theGRQ message to find the GK for registration should it not receive theMGA message.

Step 1c: In response, GK 2 sends gatekeeper confirmation (GCF) orrejection (GRJ) message.

Step 1b and 1c are an alternative to step to if the MGA message is notreceived by the mobile entity.

Step 2: The mobile terminal sends the RRQ message for registration with(visiting/foreign) GK 2. This message will contain the mobile terminal'shome and care-of network addresses (e.g., IP addresses) in addition toother information.

Step 3: (Visiting/Foreign) GK 2 sends the mobility binding updaterequest (BuRQ) message to the mobile entity's (home) GK 1.

Step 4: In response, (Home) GK 1 sends the mobility binding confirmation(BuCF) or rejection (BuRJ) message.

Step 5: (Visiting/foreign) GK 2 sends the registration confirmation(RCF) or rejection (RRJ) message to the mobile terminal.

Step 6: The mobile terminal sends the admission request (ARQ) message to(Visiting/Foreign) GK 2 as a precursor for establishment of a newconnection in its new point of attachment after receiving theregistration confirmation (RCF) message.

Step 7: (Visiting/Foreign) GK 2 sends the admission confirmation (ACF)or rejection (RRJ) message to the mobile terminal based on the factwhether the requirements for the admission can be met or not. In ACF,the GK returns a call signaling channel transport address of the fixedterminal (FT).

Step 8: The mobile terminal sends the Setup message to the fixedterminal for joining the same on-going conference (CID=K) afterreceiving the admission confirmation (ACF) message using that transportaddress of the fixed terminal. It is seeking a new connection (MT2) forthe same conference (CID=K) that was used for the previously establishedconference between the mobile terminal (MT1) and the fixed terminal(FT).

Step 9: The fixed terminal sends the Call Proceeding/Alert messageindicating that the called fixed terminal has been alerted with the newconnection (MT2).

Step 10: The fixed terminal (FT) responds with the Connect message whichcontains an H.245 control channel transport address for use in H.245signaling for the new connection (MT2). The fixed terminal withmultipoint controller (MC) will associate this new call of the newconnection (MT2) for the same conference (CID=K).

Step 11: H.245 message exchanges take place between the fixed and themobile terminal and the detail has not been shown for simplicity. Mediachannels (audio, video, and/or data) for communications between thefixed terminal (FT) terminal (having the MC capability) and the mobileterminal's new connection (MT2) are opened.

Step 12: Conversations (audio, video, and/or data) between the FT (fixedterminal) and the MT2 (mobile terminal's new connection) take place.

Step 13: The mobile terminal issues the H.245 endSessionCommand messagein the H.245 control channel, indicating to the fixed terminal that itwishes to disconnect the old call (for the old connection MT1) and thendiscontinues the H.245 message transmission.

Step 14: The fixed terminal responds with the H.245 endSessionCommandmessage in the H.245 control channel for termination of the old call(for the old connection MT1).

Step 15: Then the fixed terminal sends the releaseComplete messageindicating the old call (for the old connection MT1) has beenterminated. (It may be noted that the conference (CID=K) between thefixed terminal (FT) and the mobile terminal's new connection (MT2) isstill going on although the old connection MT1 has been released.)

Step 16: The mobile terminal sends the H.225.0 disengage request (DRQ)message to (home) GK 1 to release the resources used for the oldconnection (MT1).

Step 17: (Home) GK 1 responds with the H.225.0 disengage confirm (DCF)or reject (DRJ) message after releasing the resources used for the oldconnection (MT1).

Similar to the case of the intra-zone scenario, a new connection isestablished with the fixed terminal and the mobile terminal (MT2) acrosszones 1 and 2. The handover is provided form the old (MT1) to the newconnection (MT2) using the MC capability of the fixed terminal. It isexpected that there might be a situation where both the old and the newconnection might co-exist for a very brief period of time before thesuccessful handoff is made.

FIG. 27 shows the inter-zone communications where the call is routed viaGK 1 that has the MC capability. This case is similar to that of thescenario for the directly routed call with the fixed terminal having theMC capability. The exception is that the GK with its MC that iscontrolling the call is priori involved in the beginning of theconference. The point-to-point call between the fixed and mobile entityis being made via GK 1 (with its MC) and H.245 control channels are alsobeing established via GK 1 before the handover is made.

FIG. 27 illustrates the call signaling for the GK-routed handover. It isassumed that a point-to-point call has been established between thefixed and the mobile entity via the GK (with MC). This also implies thatH.245 control channels have also been established via GK 1 The steps 1through 15 are similar those have been shown as in the case of thedirectly routed call (FIG. 22). The exception is that GK 1 (with MC)will be involved to provide the handover from the old connection (MT1)to the new connection (MT2) instead of the fixed terminal (with MC).

Although the present invention has been described in relation toparticular preferred embodiments thereof, many variations, equivalents,modifications and other uses will become apparent to those skilled inthe art. It is preferred, therefore, that the present invention belimited not by the specific disclosure herein, but only by the appendedclaims.

What is claimed is:
 1. A computer-readable medium having computer-executable steps for implementing, by a Mobile Terminal \/Node/Entity, an H.323-based mobility protocol for real-time mobile multimedia communications and conferencing over packet-based networks wherein a plurality of H.323 mobility gatekeepers provide notification of H.323 mobility services availability by periodically broadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisement with a multicast address, comprising the computer-executable steps of: where the Mobile Terminal/Node/Entity becomes mobile and initiates an H.323 communication that includes at least one of: audio, video and data, by the Mobile Terminal/Node/Entity, with respect to notification, one of: providing, by at least one of a plurality of available H.323 Home/Foreign Mobility Gatekeepers, notification of H.323 mobility services availability by periodically broadcasting/multicasting/unicasting a Mobility Gatekeeper Advertisement with a multicast/unicast address; and where the Mobile Terminal/Node/Entity lacks notification of H.323 mobility services availability, broadcasting/multicasting/unicasting/sending, by the Mobile Terminal/Node/Entity, a message to the Home Gatekeeper/Home Location Database, which notifies H.323 Home/Foreign Mobility Gatekeepers in a preselected area local to the Mobile Terminal/Node/Entity that the Mobile Terminal/Node/Entity needs H.323 mobility services and notifying, by the H.323 Home/Foreign Mobility Gatekeepers, the Mobile Terminal/Node/Entity of available H.323 Home/Foreign Mobility Gatekeepers; registering, by the Mobile Terminal/Node/Entity, with a H.323 Home/Foreign Mobility Gatekeeper of the available H.323 Home/Foreign Mobility Gatekeepers that support H.323 mobility services in a Location Area/Cell/Zone of the Mobile Terminal/Node/Entity; and providing, for the Mobile Terminal/Node/Entity by the H.323 Home/Foreign Mobility Gatekeeper with which the Mobile Terminal/Node/Entity is registered, support for the H.323 communication that includes at least one of: audio, video and data.
 2. The computer-readable medium of claim 1 wherein registering with the H.323 Home/Foreign Mobility Gatekeeper includes sending registration information for the Mobile Terminal/Node/Entity using a Base Station to Base Station Controller to Mobile Switching Center to H.323 Home/Foreign Gatekeeper system.
 3. The computer-readable medium of claim 1 wherein Databasing with the at least one H.323 Home/Foreign Mobility Gatekeeper includes sending registration information for the Mobile Terminal/Node/Entity using a wireless/wire-line Local Area Network to Router/Switch to H.323 Home/Foreign Gatekeeper system.
 4. The computer-readable medium of claim 1 wherein registering includes the steps of: broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, a Mobility Gatekeeper Advertisement (MGA) message periodically; broadcasting/multicasting/unicasting/sending a registration request message (RRQ) to the Home Gatekeeper by the Mobile Terminal/Node/Entity; and sending, by the Home Gatekeeper, a registration confirmation/registration rejection (RCF/RRJ) to the Mobile Terminal/Node/Entity.
 5. The computer-readable medium of claim 1 wherein registering includes the steps of: upon determining, by the Mobile Terminal/Node/Entity, that a network point of attachment has changed/a foreign zone has been entered, broadcasting/multicasting/unicasting/sending, by the Mobile Terminal/Node/Entity, a registration request message (RRQ) to a Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a binding update message (BuRQ) to the Home Gatekeeper; broadcasting/sending, by the Home Gatekeeper, a binding update confirmation/rejection (BuCF/BuRJ) to the Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, the binding update confirmation/rejection to the Mobile Termninal/Node/Entity.
 6. The computer-readable medium of claim 5 wherein, where the Mobile Terminal/Node/Entity has already visited another foreign zone regulated by a Visited Gatekeeper, registering includes: broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, a mobility unbinding message (UbRQ) to the Visited Gatekeeper; and broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper, a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the Home Gatekeeper.
 7. The computer-readable medium of claim 1 wherein, where the Mobile Terminal/Node/Entity has already visited another foreign zone regulated by a Visited Gatekeeper, registering includes: broadcasting/multicasting/unicasting/sending, by the Mobile Terminal/Node/Entity, a registration request message (RRQ) to a Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a mobility unbinding update message (UbRQ) to the Visited Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper, a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a provisional registration confirmation to the Mobile Terminal/Node/Terminal and broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a binding update message (BuRQ) to the Home Gatekeeper; and broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, a binding update confirmation/rejection (BuCF/BuRJ) to the Foreign/Visiting Gatekeeper.
 8. The computer-readable medium of claim 1 wherein, where the Mobile Terminal/Node/Entity has already visited another foreign zone regulated by a Visited Gatekeeper, registering includes: broadcasting/multicasting/unicasting/sending, by the Mobile Terminal/Node/Entity, a registration request message (RRQ) to a Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper, a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a provisional registration confirmation to the Mobile Terminal/Node/Terminal and broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a binding update message (BuRQ) to the Home Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, a binding update confirmation/rejection (BuCF/BuRJ) to the Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, a mobility unbinding update message (UbRQ) to the Visited Gatekeeper; and broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper, a mobility unbinding confirmation/rejection (UbCF/UbRJ) to the Home Gatekeeper.
 9. The computer-readable medium of claim 1 wherein at least one Home/Foreign Gatekeeper utilizes a combined Home/Visitor Location Database.
 10. The computer-readable medium of claim 1 wherein a plurality of Home/Foreign Gatekeepers each utilize an individual Visitor Location Database and share a Home Location Database.
 11. The computer-readable medium of claim 1 wherein, where the Mobile Terminal/Node/Entity is originally located in a First Administrative Domain and is moving in a Second Administrative Domain, Databasing includes: broadcasting/multicasting/unicasting/sending a registration request message (RRQ), by the Mobile Terminal/Node/Entity to the Foreign/Visiting Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a mobility unbinding (UbRQ) message to a Visited Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Visited Gatekeeper, an unbinding confirmation/rejection (UbCF/UbRJ) to the Visiting/Foreign Gatekeeper; broadcasting/multicasting/unicasting/sending, by the Visiting Gatekeeper, a provisional registration message to the Mobile Terminal/Node/Entity; broadcasting/multicasting/unicasting/sending, by the Foreign/Visiting Gatekeeper, a mobility binding message (BuRQ) to a Border Element of the Second Administrative Domain, which forwards the message to a Border Element of the First Administrative Domain which then forwards the message to the Home Gatekeeper; and broadcasting/multicasting/unicasting/sending, by the Home Gatekeeper, a mobility binding confirmation/rejection (BuCF/BuRJ) message to the Border Element of the First Administrative Domain, which forwards the message to the Border Element of the Second Administrative Domain, which forwards the message to the Visiting Gatekeeper.
 12. The computer-readable medium of claim 1 wherein communication utilizes an Internet Protocol. 